You may not have known there is such an in-depth science behind designing and building your entryway. To help you select the best entryway options for you, we’ve compiled this glossary of common door terms.


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.

Astragal: The post-type fitting on the latch-side edge of one of a set of paired or double doors, which covers the margin between doors when they are closed, 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.


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.

Caulking: Sealant which is usually extruded or troweled into a recess or joint, to seal against air and water leakage through the joint.

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.

Condensation: Condensation, or "sweating," is a natural occurrence in the home and is caused by excessive humidity, or invisible water vapor, present in the air. When this water vapor comes in contact with a surface which is at a cooler temperature, the vapor turns to visible droplets of moisture. Often this harmless water vapor can be seen collecting on glass surfaces, such as windows or doorglass.

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 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.

Cylinder 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.


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.

Double-Glazed: Outfitted with two panes of glass with a sealed airspace between.

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.

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.

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.


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

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

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.


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.


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

Insulated Glass, Insulating Glass: A glass assembly of multiple full-lite pieces, separated by a perimeter spacer and sealed as a unit. Insulated glass in residential doors is usually made with two thicknesses of 1/8-inch glass, separated by an airspace up to 3/4-inch thick.

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.


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


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


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.

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 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-E Glass: Glass which has been factory coated with a thin layer of material, nearly clear, which acts to absorb and reflect heat and light energy.


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.

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.

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.


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.

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.


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.

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.

PVC: Abbreviation for polyvinyl chloride, a plastic material used to make molded or extruded parts.


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.

Rail: In insulated door panels, the part, made of wood or a composite material, which runs inside the assembly, across the top and bottom ends, and makes up the top or bottom edge. In stile and rail doors, horizontal pieces at top and bottom edges, and at intermediate points, which connect and frame between the stiles.

Reveal: The offset or margin between edges of parts.

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.

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

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.

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.

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.


Tempered Glass: Glass sheet which has been strengthened by heat processing. Tempered glass when broken, shatters into small pieces without sharp edges. See safety glass.

Thermal Break: A feature of a door or frame assembly which separates metal or glass exposed to outside temperatures, from coming into contact and transmitting heat to or from inside-exposed parts.

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

TPE: Abbreviation for thermoplastic elastomer. TPEs are used to make weatherstripping and gasketing parts.

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.

Triple-Glazed: An insulated glass assembly made of three thicknesses of glass, with air spaces between the outer and inner thicknesses.


U-Value: A number which describes in specific terms, the ability of a material or assembly to transmit heat from outside to inside surfaces. Assemblies with lower U-values transmit less heat than those with higher values. See R-value. A U-value is the inverse of an R-value.


Water Penetration: The unwanted passage of water through a door system.