Window & Door Glossary

Air infiltration — the flow of air that passes through windows and doors. On NFRC labels, the lower the number, the better.

Airspace — the space between layers of glass, often filled with argon or krypton gas.

Apron — horizontal trim board under a window stool.

Awning— a window consisting of one sash hinged at the top which projects outward from the home.

Backband — additional trim piece on the outside edge of window casing, usually installed when the casing is flat boards.

Balance — a mechanical device used in hung windows as a means of counterbalancing the weight of the sash. Common balance systems are constant force, block and tackle, and spiral.

Bay window — window that projects out from the wall, usually consisting of 3 window units with the largest unit in the center.

Bottom rail — bottom horizontal member of a window sash.

Bow window (also compass, radial bay window) — rounded bay window that projects from a wall in the shape of an arc. It consists usually of five units.

Brickmould — a moulding used as an exterior door or window casing.

British thermal unit (Btu) — the heat required to increase the temperature of 1 lb. of water 1°F.

Caming — Formed metal stripping, usually made of brass or zinc plated steel, used between cut-glass pieces to assemble the pieces into a decorative glass panel. Caming is soldered at joints to bond the glass assembly together.

Casement window — a window with one sash hinged to open from the side and project outward from the home

Casing — a trim used to cover the space between the window frame or jamb and the wall.

Chemically bonded (when related to a welded corner) — a process where the two polymer profiles or pieces are heated and fused together with the aid of a chemical reaction. The reaction and bonding is similar to the original extrusion process.

Cladding — material that covers the frame, sash, or sliding door panel exteriors and make a weather-resistant surface.

Condensation — deposits of moisture (water droplets or frost) on the surface of an object caused by warm, moist air coming into contact with a colder surface.

Corrosion — deterioration caused by chemical or electrochemical reactions resulting from exposure to weather, moisture, chemicals, or other harmful materials.

Design pressure (DP) — a rating that identifies the wind load that a product is rated to withstand in its end-use application, measured in pounds per square foot (psf).
Note: Design pressure (DP) is not to be confused with Performance Grade (PG) or structural test pressure (STP).

Divider — a member that divides the glass area of a window into separate areas. Dividers are either structural or decorative. Other common terms are muntin, true divided lite (TDL), simulated divided lite (SDL), grill, grid, or bar-in-glass.

Dormer window — window in a wall that either projects from a sloping roof, or is recessed (inset dormer) into the roof, or a combination of both.

Double-hung window —window with two sashes that can move vertically past each other to allow venting.

Drip cap — horizontal exterior molding to direct water from the top of the window or door unit so water drips beyond the outside of the frame.

Dual pane (Dual glazing) — two layers of glass separated by a spacer and airspace, and sealed.

Egress — window that is required in sleeping locations in a home and is intended to provide emergency escape and rescue access. Windows must meet specific size and requirements to qualify as an egress window. Requirements are defined by local building codes.

ENERGY STAR® — a U.S. Environmental Protection Agency (EPA) voluntary program that helps businesses and individuals save money and protect our climate through superior energy efficiency.

Escutcheon plate: decorative plate behind a door handle that conceals the locking mechanism.

Extension jamb (also jamb lining and jamb extender) — a board used to increase the depth of the jambs of a window frame to fit a wall of any given thickness.

Fenestration — openings in the building envelope, such as windows, doors, secondary storm products (SSPs) curtain walls, storefronts, roof windows, tubular daylighting devices (TDDs), sloped glazing, and skylights, designed to permit the passage of air, light, or people.

Fixed window — a window that is designed to be non-operable and consists of a glazed frame or a non-operating sash within a frame.

Flashing —a strip of water-resistant material that diverts water away from a window or door.

Forced-entry resistance (FER) — the ability of a window or door in the locked position to resist entry under a specified load and conditions.

Frame — the enclosing structure of a window or door, which fits into or attaches to the wall opening.

Full frame — type of installation which requires the frame of the old window to be completely removed, allowing the new window to be installed into the studded wall opening.

Fusion welded — when materials are fused by heating the edge and pressing the two pieces together. When cooled, they become one piece.

Garden window — a window consisting of a three-dimensional, five-sided structure, often with shelves for plants in the enclosed space that protrudes outside the home.

Glazing — (n): glass in a window sash or door panel. (v): the process of installing glass in windows and doors

Glazing bead (also glass stop and wood stop and sill bead) — removable trim that holds glass in place.

Handing — opening direction of hinged windows and doors; direction is determined by location of hinge on unit as viewed from exterior

Handle — a component which enables the movement of a sash or panel, or which activates a mechanism which locks or unlocks a sash or panel.

Hardware — all the necessary equipment to retain, operate, and lock or unlock the sash or panel within the frame.

Head — the horizontal member forming the top of a window or door.

Header (also lintel; beam) — horizontal member (wood, steel, or stone) over a window opening to support the weight of the wall above. The term header is generally in reference to a wood beam, whereas “Lintel” often refers to a steel beam.

Hopper window —a window consisting of one sash hinged at the bottom which opens inward from the frame.

Insulating glass unit (IG unit or IGU) — two or more panes of glass spaced apart with a perimeter spacer and hermetically sealed to form a single unit with an air- or gas-filled space between each pane.

Jambs — the upright or vertical members forming the sides of the frame.

Jamb depth — width of the window or door frame from inside to outside.

J-Channel: installed or built-in to the side of a window or door, this channel is designed to accommodate the ends of siding pieces to provide a finished appearance.

Keeper — hardware on a sash that receives and engages with lock

Laminated glass — two or more panes of glass with an inner layer of transparent plastic to which the glass adheres if broken. Used for enhanced safety and security, as well as sound reduction.

Lite — a pane of glass or an insulating glass (IG) unit used in a window or door.

Low-emissivity (Low-E) glass: glass with a coating that reflects heat.

LRRP — the lead paint Renovation, Repair and Painting program established by the Environmental Protection Agency for pre-1978 homes to address health and safety issues associated with lead paint. Firms involved in such projects must be trained and certified in lead-safe work procedures. Also referred to as RRP. Information available on EPA Web site.

Meeting rail or check rail — one of the two adjacent horizontal sash members that come together when in the closed position.

Mulling — the process of joining two window or door units together

Mullion — component used to structurally join two window or door units. The joint can run vertically or horizontally.

Multi-point lock — a lock operated with one handle that engages the sash or panel in multiple locations

Muntin — see Divider.

Nailing fin — An accessory component or integral extension of a window or patio door frame that generally overlaps the conventional stud construction. Nails can be driven through it to secure the frame in place.

Negative pressure — pressure acting in the outward direction.

NFRC — National Fenestration Rating Council. A body that has established methods for rating and certifying the energy performance of windows, doors, skylights and other fenestration products.

Obscure glass — see Privacy Glass

Operator — hardware designated to open and close hinged windows and blinds.

Outdoor-indoor transmission class (OITC) — a single-number rating that provides an estimate of the sound insulation performance of windows and doors. Note: The frequency range used is typical of outdoor traffic noises.

Panel — the members of a sliding door or sliding door side lite within a frame which are designed to accommodate the glazing.

Parting bead (also parting strip and parting stop) — a vertical strip on each jamb that separates the sashes of a double-hung window and holds the sash in place.

Performance Grade (Grade or PG) — an industry rating for a unit that has been tested for air, water, structural and forced entry performance. Often a factor of compliance with local building codes.
Note: Performance Grade (Grade or PG) is not to be confused with design pressure (DP) or structural test pressure (STP). Performance Grade (PG) is achieved only on successful completion of all applicable tests specified

Picture window — large fixed windows.

Privacy Glass — glass with an irregular surface for scattering light; used for privacy or to reduce glare.

Pocket window — type of installation which the sashes and jamb tracks are removed, and a new window installed within the old frame.

Positive pressure — pressure acting in the inward direction.

Projected Frame window — window with a frame with extended jambs and projects outward from the home.

Rail — a horizontal member of a sash or panel.

Reinforcement — the material added to individual sash, panel, or frame members to increase strength and/or rigidity.

Rough opening — a structurally-framed opening in a wall which receives a door unit or window.

R-value: numerical rating designating the resistance to thermal transfer or heat flow. Higher R-value numbers indicate greater insulating value. R-value is frequently used by the insulation industry and is the reciprocal of U-factor, a value more generally used in the window industry.

Safety glass — a strengthened or reinforced glass that is less subject to breakage or splintering, such as glass for doors and some windows. See also Tempered glass and Laminated glass.

Sash — an assembly of stiles and rails (vertical and horizontal members) made into a frame for holding glass.

Screen — a product that is used with a window or door consists of a mesh of wire or fiberglass attached to a frame to keep out insects. It is not meant for providing security or retention of objects or persons from the interior.

Seal — material around the edge of an insulated glass unit that protects the glass unit from air and water leakage.

Sidelite — an operable or non-operable product that is designed to be a companion product installed on one or both sides of an operable door or a fixed door.

Sill (also sill plate; inside sill; outside sill) — horizontal member at the bottom of the window or door frame

Simulated divided lites (SDLs): A type of grille or grid design that creates the appearance of a number of smaller panes of glass separated by muntins, but actually uses larger lites of glass with the muntins placed between and/or on the surfaces of the glass layers.

Single glazing — glazing that is just one layer of glass or other glazing material.

Single-hung window — a hung window with only one operable sash.

Slider — a window that consists of one or more sashes that slide or roll horizontally within a common frame and can also contain fixed lites/sash.

Sliding door — a door that consists of manually operated door panels, one or more of which slide or roll horizontally within a common frame, and can also contain fixed lites/panels.

Solar heat gain coefficient (SHGC) — a rating measuring a window’s ability to transmit solar heat. It measures both the solar radiation which is directly transmitted, as well as the solar radiation absorbed by the glass and subsequently transmitted. The lower a unit’s solar heat gain coefficient, the less solar heat it transmits. It is expressed as a number between 0 and 1.

Sound transmission class (STC) — a rating measuring a window’s acoustic properties or its ability to reduce sound transmission. An STC rating is determined by measuring the sound transmission over a selected range of sound frequencies. The higher the number, the less sound transmitted.
Note: The frequency range used is typical of indoor office noises.

Spacer — the linear material that separates and maintains the space between the glass surfaces of insulating glass units.

Stile — a vertical member of a sash, leaf, or panel.

Stool— a horizontal board or trim piece at the windowsill on the inside of the window, fitted against the bottom rail of the lower sash to form a base for the casing.

Storm window — that window in a dual-window unit so designated by the manufacturer, used on the exterior of, or interior of, and in tandem with, a primary window for the purpose of performance enhancement, and not to be used by itself as a primary window.

Structural test pressure (STP) — the pressure differential applied to a window or door system.
Note: Structural test pressure (STP) is not to be confused with design pressure (DP) or Performance Grade (PG).

Tempered glass — glass that has been heat-treated to make it strong. If broken, it will fracture into small pieces without sharp edges. Tempered glass is approximately four times stronger than annealed glass of the same thickness.

Thermal barrier — an element made of material with relatively low thermal conductivity, which is inserted between two members having high thermal conductivity, in order to reduce the heat transfer.

Transom — an operable or non-operable product that is designed to be a companion product installed above a window or door.

Triple pane — three panes of glass separated by two spacers and air-spaces.

U-factor — rate of heat flow-value through a building component, from room air to outside air. Also referred to as U-value. The lower the U-factor, the better the insulating value.

Weatherstrip (weatherseal) — a flexible component used to reduce air leakage, water penetration, or both between sash and/or frame.

Weephole (weep) — an opening that allows water to drain.

Active — In paired or double doors, the hinged door leaf which is primarily operable.

Affidavit Label — For fire-rated doors, a label on a door product on which the manufacturer, not an independent laboratory, states that the door meets a type or types of test criteria.

Air Infiltration — Air passing through a door system when the door is under pressure, usually from wind.

Annealed Glass — Regular glass which has not been heat strengthened or tempered. Most window glass is annealed.

Astragal— The post-type fitting on the latch-side edge of one of a set of paired or double doors, which covers the gap between doors when they are closed, prevents swing through, and which houses or contains the weatherstrip.

Backset — For locating a machined hole, recess, or mortise, the distance from an edge or surface to the center or edge of the recess, hole or mortise.

Ball-bearing Hinge — A heavier-duty hinge than the standard hinge, with bearings supporting the pivots. Ball-bearing hinges are usually used for heavy doors that will be in commercial or industrial use.

Barbed — An adjective that describes the feature of a part which inserts into a slot, and which has surface features that enable it to stay firmly inserted into the slot.

Boot — A term used for the rubber part at the bottom or top end of an astragal, which beds the astragal end and seals between the end and the door frame or sill.

Boss, Screw Boss — A feature of a part which enables the fastening of a screw into the feature, thereby allowing assembly of the part with another. Screw bosses are common features of molded plastic lite frames and extruded aluminum door sills.

Box-Framed— In door and sidelite assemblies, a term used to differentiate door and sidelite units which are first framed as separate units, with heads and sills separate and the width of the door or sidelite panels. Box-framed doors are joined to box-framed sidelites.

Brad— A small nail with a small head, usually used to fasten small trim and moldings.

Brickmould—A molding, used to trim the outside edge of a door frame. Brickmould is most often applied to prehung units.

Buck—A term usually used in masonry construction to describe a door frame or a subframe in a masonry opening, around which a steel door frame wraps and is fastened.

Butt—A type of hinge commonly used to assemble doors. Butt hinges are often referred to as simply butts.

Butyl—An organic compound, used in the door business as a sealant. It is naturally black, and is heated and pumped through nozzles, or pumped cold.

Bevel—A machine angle other than a right angle, i.e., a 3 degree bevel that is equivalent to a 1/8 inch drop in a 2 inch span (1 mm in 16 mm).

Blister—Spot or area where veneer does not adhere.

Blocking—A material used to replace core material in specific locations to provide improved screw holding for the attachment of hardware. Blocking is only required where the screw holding power of the core is less than required by the applicable performance duty level.

Bow— a curvature along the length of the door.

Bullet Resistant Doors—Doors that resist penetration by shots of varying caliber. Resistance may be rated as resistant to medium power, high power, or high power small arms and high power rifles.

Butt Joint—A joint formed by square edge surfaces (ends, edges, and faces) coming together; end butt joint, edge butt joint.

Came, Caming—Formed metal stripping, usually made of brass or zinc plated steel, used between cut-glass pieces to assemble the pieces into a decorative glass panel. Caming is soldered at joints to bond the glass assembly together.

Carpet Shim—A spacer block used under a door sill to raise the sill an appropriate amount if carpet is used, so the door panel clears the carpet when opened.

Casing—A horizontal or vertical molding, which accents or trims edges of doors and windows to the surrounding walls. Casing also covers or accents intermediate posts.

Clad—Provided with a facing or jacket which works as a protection against weather, and provides a finished appearance. Cladding may be painted metal, plastic, or a heavy coating applied by the manufacturer.

Clear Jambs— Natural wood door frames, without paint or primer applied, and which appears to be made of full-length pieces of stock, without joints or knots.

Closed-Cell Foam—Sponge-like material, usually used in gaskets and weatherstripping, which compresses into joints, but absorbs little water.

Closer Block— An inside reinforcement, usually placed across the top edge of a door, to enable firm fastening of self-closing hardware to the door.

Continuous Sill—A sill used for a type of door and sidelite unit in which the unit has full width top and bottom frame parts, and an internal post or posts separating sidelites from the door panel.

Core—The center section or part of a door or door part.

Corner Plug, Corner Seal Pad—A small part, usually made of resilient material, used to seal water which gets beyond the bottom ends of weatherstrip in doors, from getting between the door edge and the jambs, adjacent to the bottom gasket.

Cove Molding—A small molded wood lineal piece, usually formed with a scooped face, used to trim and fasten a panel of some type into a frame.

Crossbore—A large through-hole, near the edge of a door panel, usually 2-1/8 inch in diameter, which houses a cylinder lockset or deadbolt latch.

Cylinder Lock, Cylindrical Lock—Lock hardware which mounts into a door which has been prepared with a bored hole or holes through the face, and into the edge.

Component —An individual piece that is joined to other pieces to achieve a full system.

Deadbolt—A latch used to secure a door closed, the latch being driven from the door into a receiver in the jamb or frame.

Deflection—The distance a door has moved away from its closed and latched position, usually measured at the top unsupported latch-side corner. Deflection may be caused by wind pressure or heat. Deflection is temporary. The door returns to position when the force is removed.

Desiccant—Moisture absorbing material used inside the spacer in an insulated glass assembly, so as to control moisture levels and prevent moisture from frosting or condensing on the inside glass surfaces of the insulated unit.

Doorlite—An assembly of frame and glass panel, which when fitted to a door in a formed or cut-out hole, creates a door with a glass opening.

Door Frame—A group of components (wood, aluminum or steel) that are assembled to form an enclosure and support for a door. Also known as door jambs.

Door, Bifold—Doors so hinged as to fold against the door jamb. Bifold doors are normally classified as either two- or four-leaf units.

Door, French—A door assembly of stiles and rails (and possibly muntins and bars) surrounding a single or multiple glazed opening.

Door, Panel—A door assembly of stiles, rails and one or more panels. Intermediate rails or mullions are used to separate panels. Panels can be raised or flat.

Dual Glazed—Outfitted with two panes of glass with a sealed airspace between.

Drip Strip—In exterior doors, a fitting used across the outside face of the door adjacent to the bottom edge, to divert cascading rain away from the door bottom edge and away from the door/sill joint.

Drywall Opening—A rectangular opening in a wall, usually an interior wall, prepared to the size necessary to receive a pre-hung assembly.

Dummy Cylinder: A lock without a latch, typically used for the passive door panel of a double door unit, so that the hardware appears equal to that used on the active panel.

Edge Bore—The hole bored through the edge of a door to allow the latch to pass through, into the strike.

Electric Strike: A mechanism which allows a switch to open the latch of a door.

End Seal Pad—A closed-cell foam piece, about 1/16-inch thick, in the shape of a sill profile, fastened between the sill and the jamb to seal the joint.

Escutcheon: A stamped decorative plate, usually circular to trim the shaft of a door knob or deadbolt latch, to trim the opening where the shaft or latch adjoins the face of a door.

Etched Glass—Glass used for doorlites on which a decorative pattern is engraved by means of chemical action or mechanical sand-blasting.

Extension Unit—A framed fixed door panel, with a full-sized lite of glass, field-installed or shop-installed adjacent to a two-panel patio door, to make the door unit into a three-panel door.

Faceplate—The plated or solid metal trim piece, usually about 1 x 2-1/4 inches, housed flush into the edge of a door, through which projects the latch of a passage lock or deadbolt.

Finger Joint—A way of joining short sections of board stock together, end to end to make longer stock. Door and frame parts are often made using finger-jointed pine stock.

Fire Door—A door of a construction type which has been tested to contain the spread of fire from one room or occupancy area to another. Fire doors are listed and labeled to show their ratings in terms of time, i.e., 20-Minute, 90-Minute, etc.

Finger Joint—A series of interlocking fingers precision cut on the ends of two pieces of wood which mesh together and are held rigidly in place with adhesive.

Fire Rated Doors—A door which has been constructed in such a manner that when installed in an assembly will pass a fire test under neutral (UL 10B) or positive (UL 10C) pressure criteria and can be rated as resisting fire for 20 minutes (1/3 hour), 45 minutes (3/4 hour), 1 hour, or 1-1/2 hours. The door must be tested and carry an identifying label from a qualified inspection agency.

Flush-Glazed—A type of glazed door which has its glass perimeter moldings flush with or set down from the face of the surrounding door.

Foam—Rigid or flexible plastic, light in weight and cellular in structure, used in door construction. Rigid foam is used as the insulating and binding core for doors. Flexible foam is sometimes used as gasket.

Foot Bolt—A steel pin housed in a door bottom edge or astragal, with a latch mechanism, which can be driven down to project into a receiver socket or hole in the floor or threshold, to better secure the door when closed.

Frame—In door assemblies, the perimeter members at the top and sides, to which the door is hinged and latched. See jamb.

Galvanized—An adjective used to describe steel which has been zinc-coated. Galvanized steel is resistant to corrosion.

Gasket—A strip of flexible material which in an assembly of parts, prevents air and water from penetrating or passing through joints between parts.

Glass Stop—A small wood moulding (bead) applied to the perimeter of glazed openings to secure the glazing materials within a door.

Glazing—The elastic material used to seal glass to a surrounding frame.

Grain—The direction, size, arrangement and appearance of the fibers in wood.

Grille—For doors with glass lites or inserts, a removable face-mounted assembly of thin wood or plastic pieces, which when in place, gives the lite or insert a patterned multi-pane look.

Grooved Glass—Glass which has been decorated with abrasively-routed recesses. Grooving can give a single piece of glass a multi-paned look.

Handing—A term which describes or determines the direction of swing of a door when opening.

Head Bolt—A steel pin housed in a door top edge or astragal. See foot bolt.

Head, Head Jamb—The horizontal top frame member of a door assembly.

Hinge—An assembly of metal plates and a cylindrical metal pin, which when fastened to a door edge and to a door frame, allow the door to swing or rotate in its frame.

Hinge Stile—The full-length vertical edge of a door, at the side or edge of the door which fastens to its frame with hinges.

Horned Sill—A sill which has been coped or cut in such a way at its ends, so that the sill projects across the outside face of the bottoms of door jambs, allowing the bottom ends of the brickmold pieces to butt and join to the top of the sill.

Inactive—A term for a door panel fixed in its frame. Inactive door panels are not hinged and are not operable.

Inswing—A term used to describe an exterior entry door unit for which, when the hinged door panel is opened, the panel swings into the building.

Insulating glass unit (IG unit or IGU) — two or more panes of glass spaced apart with a perimeter spacer and hermetically sealed to form a single unit with an air- or gas-filled space between each pane.

Intumescent—A material that expands when exposed to extreme heat or fire to fill any gap between the door and frame or between doors.

Jamb— A vertical perimeter frame part of a door system.

Jamb Jack — A fastener device for fixing a door frame to a wall structure, which allows the space or margin between the frame and the structure opening, to be varied by turning the fastener screw.

Jamb Stop — In exterior door frames, the molded-in rebate surface of a frame member against which door panels close and seal.

J-Channel — installed or built-in to the side of a window or door, this channel is designed to accommodate the ends of siding pieces to provide a finished appearance.

Kerf — A thin slot cut into a part with a molder or saw blade. Weatherstrip is inserted into kerfs cut into door jambs.

King Stud — In a wood-framed rough opening, the stud which runs full height from floor plate to ceiling plate, against which trimmer stud attaches.

Knuckle — The feature of a hinge where the hinge leaf is cut for two or three projections which wrap and form a barrel or socket for the hinge pin.

Lock Block—A concealed block the same thickness as the door stile or core which is adjacent to the stile at a location corresponding to the lock location and into which a lock is fitted.

Latch — A moveable, usually spring-loaded pin or bolt, which is part of a lock mechanism, and engages a socket or clip on a door jamb, retaining the door closed.

Leaf — A term which can apply to a door or hinge and which defines a part of the assembly which can swing on a pivot. Butt hinges have two leaves.

Lite — a pane of glass or an insulating glass (IG) unit used in a window or door.

Lock Block — A rectangular block of wood or other solid material, placed inside a door assembly at the lock side edge, which reinforces the assembly when the lock hardware is installed.

Lock Bore — For cylindrical locksets, the large through hole, usually 2-1/8-inches in diameter, bored near the door panel’s lock edge, into which the lock mechanism is placed and installed.

Lock Rail —An intermediate rail located at approximately adjacent to the lock.

Lock Stile — In insulated door assemblies, the full-length part, usually wood, which makes up the lock edge of the door panel. In wood stile and rail doors, the full length wood piece, 4 to 6-inches wide, at the lock edge of the door.

Low-emissivity (Low-E) glass — glass with a coating that reflects heat.

Miter — An angled cut across the end of a lineal part, usually done to join with a similarly-cut part at a corner.

Mortise — A recess cut into the surface or edge of a part, usually for the purpose of housing hardware such as hinges and lock parts.

Mortise-Type Lock — A lockset which usually has a rectangular-shaped mechanism, which is housed into a deep recess cut into the edge of a door.

Mull — A short term for mullion. Used occasionally as a verb to describe the joining of two door units together, or the joining of a door to a sidelite unit.

Mulled — An adjective describing a door and sidelite unit which has been made up by edge-joining two framed units together.

Mullion — A post or divider which runs from sill to frame top in a multi-panel door, door, or door and sidelite assembly. In stile and rail doors, the vertical wood parts which separate panels.

Multiple Extension Unit — In patio door assemblies, a fixed door panel in a separate frame, edge-joined to a patio door unit to add another glass panel to the installation.

Muntins — In glazed lite assemblies, thin vertical and horizontal divider bars, which give the lite a multi-paned look. Muntins may be part of lite frames, and on the outside surface of the glass, or assembled between glass in insulated glass units.Moulding (Inlay)—Profiled wood trim pieces that surround the perimeter of panels or glazing, but does not protrude above the surface of the surrounding stiles and rails.

Moulding (Overlay)—Profiled wood trim pieces that surround the perimeter of panels or glazing, and protrudes above the surface of the surrounding stiles and rails.

Mullion—A vertical member used to separate panels. Also known as a “mull”.

Muntin—A short bar, either horizontal or vertical, used to separate individual pieces of glazing material, but which does not extend the full width or length of the glazed opening. Also known as “munt”.

Neutral Pressure—A fire door test procedure where the neutral pressure plane is near the top of the door.

Nailing Fin — A feature of some windows and patio doors which permits installation and fastening to a rough opening by nails or screws driven through the fin at the top and side edges of the unit, into the surrounding frame of the opening.

NFRC— Initials for National Fenestration Ratings Council, an industry association which sets standards for testing, rating, and labeling doors and windows with heat transmission and energy information.

Night Latch — A lever or knob-actuated bolt for fastening a door more securely at night.

Nosing — An edge piece, usually molded with a rounded face or corner, which runs the length of an assembly. Oak adjustable sills have a nosing part along the floor line at the inside edges.

NRP Hinge — An abbreviation for a hinge with a non-removable pivot pin. NRP hinges are used when exterior doors swing out, as a security feature. The fixed pins make it impossible to remove a door by driving out pivot pins.

Occasional—A small number of characteristics that are arranged somewhat diversely within the face.

Open-Cell Foam: A foam material which has passageways between cells. Open-cell foam will absorb and retain water, because the water will penetrate deeply inside the foam.

Outswing: An exterior door assembly in which the door panel swings outside the building.

Panic-proof Lock—A lock and latch device which permits a door to be opened outward by pressure being applied to a bar mounted across the inside face of the door.

Passage Lock—A lockset which will retain a door closed, but which cannot be locked.

Passive—In a double or two-panel door assembly, the door which usually remains closed and fixed by bolts at top and bottom. The other door panel is used for regular passage.

Plant—A decorative molding applied to the surface of a flush door, to give the appearance of a raised-molding design.

Plates—In residential wood-frame construction, the horizontal parts of a wall frame running atop the subfloor, and at the ceiling atop the stud ends, on which framing from above bears.

PVC—Abbreviation for polyvinyl chloride, a plastic material used to make molded or extruded parts.Positive Pressure—A fire door test procedure where the neutral pressure plane is located at 40 inches (1 m) above the sill.

Prefitting—Trimming of the door for width and/or height.

R-Value—A number which describes in relative terms, the ability of a material or assembly to resist the flow or transmittance of heat. Assemblies or materials with high R-values are better insulators than those with lower R-values.

Rabbet, Rebate—A rectangular recess cut or formed along the long edge of a part, usually a wood part.

Rail — a horizontal member of a door panel which fits between the stiles..

Ramp: In a sill or threshold, the horizontal face which is sloped.

Reveal: The offset or margin between edges of parts.

Riser: A term which describes the part of an adjustable sill which can be moved up or down by turning adjusting screws.

Rough Opening: A structurally-framed opening in a wall which receives a door unit or window.

Saddle—In adjustable sills, another term for riser. Also, a shop-applied label applied around the corner or edge of a door, which provides identification and installation instructions.

Safety glass — a strengthened or reinforced glass that is less subject to breakage or splintering, such as glass for doors and some windows. See also Tempered glass and Laminated glass.

Screen Track — A feature of a door sill or frame head which provides a housing and runner for rollers, to allow a screen panel to slide from side to side in the door. Scribe: A mark for a cut which has been made by using a template or pattern.

Self-Cased — A steel frame for which the edge detail finishes to the surrounding wall, without the need for additional applied casing molding.

Self-Locating Hinge — A hinge with indexing or locating tabs to aid in exact placement against a door edge.

Shim — A thin piece of material used between parts of an assembly, to change and fix the distance between parts, when parts are fastened.

Sidelite — A fixed narrow panel, installed next to a door panel, for decorative purposes. Sidelites almost always contain glass lites.

Sill Saddle — See riser.

Slide Bolt — The part of an astragal assembly which, by means of moving latches at tops and bottoms of astragals, places bolts into frame heads and sills, for fixing passive door panels closed.

Smoke & Draft Door — Where building codes define use, a fire door which has been rated for 20-minutes fire resistance, and which does not need test certification as having passed the hose stream portion of the fire test.

Spacer, Glass Spacer — A lineal part with rectangular cross section, running along the perimeter edges, between the glass pieces of an insulating glass unit.

STC — Abbreviation for sound transmission coefficient. A value which describes in relative terms the ability of a door to dampen the passage of noise. Doors with higher STC values permit less noise to pass through.

Stile — In insulated door panels, the full-length parts, usually wood, which make up the long edges. In stile and rail doors, the vertical edge parts.

Strike— A metal part with a hole or recess for receiving a door latch, also with a curved or ramped face so a spring-loaded latch contacts it when closing. Strikes are fit into mortises in door jambs or mullions, and screw-fastened.

Style— A number or name defining a door design or configuration.

Subfloor — The concrete or wood floor surface lying under the finished floor. Prehung door assemblies are installed atop the subfloor.

Substrate — The base or core material in an assembly of parts. In sills, the full length wood or composite part of the sill, visible only from the bottom side, or ends.

Safety Glazing Materials—Glazing materials so constructed, treated or combined with other material as to minimize the likelihood of cutting or piercing injuries resulting from human contact with the material. The most common types used in doors are tempered or laminated. Safety glazing materials are required to meet codes and federal regulations.


Skin—The face layer of a flush or stile and rail door, whether flat or configured, which is used for facings for flush wood doors.

Sound Transmission Class (STC)—A single number rating system derived from measured values of sound transmission loss or the acoustical performance of a building element, such as a door, window or wall. The higher the STC value, the better the rating and the better the acoustical performance value. Tested in accordance with ASTM E413 and E90.

Standard Door—By industry practice, a standard door is book size in both width and height.

Stile—The outermost vertical member of a stile and rail door.

Stiles/Vertical Edges—The upright or vertical pieces of the core assembly of a wood flush door.

Structural Composite Lumber Core (SCLC)—An engineered wood product that is made by fusing a network of wood strands together with a water-resistant adhesive to produce a strong, solid and stable product that has true structural properties with excellent screw holding properties and very high split resistance.

Sweep —A door sweep is a small piece of plastic or rubber, attached to an aluminum carrier strip and fitted across the bottom of a door. It provides a weatherproof seal and prevent drafts from coming in under the door.

Tempered glass — glass that has been heat-treated to make it strong. If broken, it will fracture into small pieces without sharp edges. Tempered glass is approximately four times stronger than annealed glass of the same thickness.

Thermal barrier — an element made of material with relatively low thermal conductivity, which is inserted between two members having high thermal conductivity, in order to reduce the heat transfer.

Threshold — Another term for sill. The horizontal part of a door assembly, fixed under the door panel and bearing on the floor.

Tinted Glass — Glass made with a green, gray or bronze tint, so as to reduce light transmittance.

Transom— A framed glass assembly mounted atop a door assembly. Transoms are rectangular in shape or have curved or arched tops. One design of a curved top transom has the shape of a half-ellipse.

Transport Clip — A steel piece used to temporarily fasten a prehung door assembly closed for handling and shipping, which maintains the door panel’s proper position in the frame.

Trimmer Stud — In a wood-framed rough opening, the stud or framing member which runs vertically from the subfloor to and supporting the structural header member, into which a door frame is fastened.

Triple pane — three panes of glass separated by two spacers and air-spaces.

Transom —The panel above a door or set of doors.

Twist—A deviation in which one or two corners of the door are out of plane with the other corners of the door.

U-factor — rate of heat flow-value through a building component, from room air to outside air. Also referred to as U-value. The lower the U-factor, the better the insulating value.

Urethane — A plastic material made by reacting two polymers. A urethane part will burn, but it will not melt.

Warp —Any distortion in the plane of a door itself and not its relationship to the frame or jamb in which it is to be hung. The term warp includes bow, cup and twist, which are defined as follows: Bow-A flat wise deviation from a straight line drawn from top to bottom; a curvature along the length of the door. Cup-A deviation from a straight line drawn from side to side; a curvature along the width of the door. Twist-A deviation in which one or two corners of the door are out of plane with the other corners of the door.

Warp — A permanent curvature or deviation from straightness, which can be induced in a part or assembly by a load or force, or by exposure to heat or moisture.

Wired Glass — Glass made for use in fire doors, which has embedded wires which bind the glass, and permit the glass to remain monolithic when exposed to fire.

Wood Filler—An aggregate of resin and strands, shreds, or flour of wood, which is used to fill openings in wood and provide a smooth, durable surface.