Door Dictionary (A–Z)
 

A
 
Active leaf – The leaf in a pair that carries the latch/locks and is used first.
 
Architrave – Decorative trim that covers the joint between the frame and wall.
 
 
Astragal / Meeting stile trim – The overlap piece fitted where two leaves meet to improve smoke/air/light control and privacy.
 
Automatic drop seal – Spring-loaded seal recessed in the door bottom; drops to the floor when the door closes to control smoke/sound. (guide)

 
B
 
Backcheck (closer) – Hydraulic resistance that slows a door near fully open to stop it being flung against walls.

Backset (lock) – Distance from forend edge to follower/cylinder centre. Critical when specifying DIN locks. (guide)

Bathroom lock (DIN) – Combined latch + privacy deadbolt operated by thumbturn/emergency release; usually 78 mm centres.

Bead / Glazing bead – Timber or metal trim that retains vision-panel glass.

Bolt (deadbolt) – The solid square/rectangular bolt that projects from a deadlock or the dead part of a sashlock.

BS 8214 – UK code of practice for installing timber fire door assemblies. Use it for tolerances, fixings and sealing. (see British standards) 

BS EN 1634-1 / -3 – European test methods for fire resistance and for smoke control of door assemblies. (see British standards) 

Brush seal – A flexible pile (often with fin) used for smoke/air sealing around a
door.

 
C
 
Case (lock case) – The body of the mortice lock that is recessed into the door.

Centres (lock) – Distance between follower centre and cylinder/turn centre (e.g., 72 mm or 78 mm on DIN).

CE / UKCA marking – Legal conformity marks for certain hardware (e.g., EN 1154 closers, EN 1935 hinges).

Clear opening width/height – The usable passage size when the door is open—what matters for accessibility.

Closer (door closer) – Device that closes the door from any angle; overhead, concealed or floor spring.

Closing force (EN 1154) – The power “size” setting of a closer (e.g., Size 3–5).

Concealed closer – Closer morticed into the leaf or frame to keep hardware hidden.

Coordinator (pair doors) – Device that ensures the correct closing sequence of active and inactive leaves (important with rebated pairs).

Cylinder (Euro profile) – Keyed cylinder that operates the deadbolt in locks such as DIN sash/deadlocks.

 
D
 
Deadbolt / Deadlock – Locking bolt thrown by key/turn; no bevel; resists back-pressure on the latch.

DIN – Deutsches Institut für Normung; in this context, the family of standardised lock cases used across the UK/EU. (guide)

Door leaf – The moving part of a door assembly.

Door set / Doorset – Factory-matched door, frame and essential hardware, supplied/tested as one assembly.

Drop seal – See Automatic drop seal.

 
E
 
Edge clearance – The designed gaps between leaf and frame (jambs/head) and the undercut to floor.

EN 1154 / 1155 / 1935 / 1125 / 179 – Common hardware standards: closers, electrically-powered hold-open devices, hinges, panic exit devices, and emergency devices.

Escape hardware – Push bars/plates that allow quick egress (EN 1125 panic; EN 179 emergency).

 
F
 
Faceplate / Forend – The visible metal plate on the lock’s edge that screws to the door.

FD30 / FD60 – Nominal 30/60-minute fire resistance classifications for doors tested to BS 476-22 or EN 1634-1. 

Follower (lock) – Square hole in the lock case that takes the spindle for the lever handles.

Frame (door frame) – Jambs and head fixed to the wall opening; carries the stop and hardware.

Free-swing closer – Closer that lets the door feel “weightless” in use but will close on alarm/power signal.

Fire/smoke seal (intumescent & brush) – Intumescent expands in heat; brush or fins restrict cold smoke. Always follow the door’s certificate.

 
G
 
Gaps (tolerances) – Designed clearances at jambs/head and undercut; must match certification and BS 8214 guidance. (guide) 

Grade (hinge) – EN 1935 hinge grade (e.g., Grade 13) indicates load/door-mass and suitability for fire doors. 

 
H
 
Handing (locks/doors) – Left/right orientation. DIN handing is based on the direction the door opens away from you on the hinge side.

Head – The top member of the frame.

Hold-open – Mechanical or electromagnetic device that holds a door open; use only where allowed by fire strategy.

 
I
 
Inactive leaf – The secondary leaf in a pair; may be fixed with flush bolts.

Intumescent (strip or pads) – Heat-activated material used around leaf/frames and behind hardware to maintain fire performance.

Installation packers/shims – Non-compressible spacers used to plumb and fix frames before sealing with approved materials.

 
J
 
Jamb – The vertical members of the frame.

 
K
 
Keeper / Strike / Strike plate – The frame-side plate or box that receives the latch and deadbolt. (calc)

Key-override – The ability to unlock a thumbturn cylinder with a key from the outside.

 
L
 
Latch / Latchbolt – The bevelled spring bolt that holds a closed door shut; works with the handle spindle.

Latch keeper – Strike designed specifically for the latchbolt (no deadbolt box). (calc)

Leaf (door leaf) – See Door leaf.

Lock case – See Case.

Lock rebate kit – Kit that adapts a lock and keepers for rebated meeting stiles on pairs.

 
M
 
Meeting stiles – The vertical edges where two leaves meet; can be square, rebated, or fitted with an astragal.

Mortice – A recess cut into the door or frame to house hardware like locks, hinges or closers.

Mineral wool (rockwool) – Non-combustible infill used around frames to seal/pack the gap between frame and wall (where permitted by certification). (guide)

 
N
 
Night latch (DIN) – Latch only (no deadbolt) typically used with cylinder; allows locking by key/knob/turn. (calc)

Nominal size – The size the product is labelled by; finished sizes can be slightly different based on tolerances.

 
O
 
Opening direction – Inward/outward; left/right—define for lock handing and closer arm selection.

Over-rebate – The overlap on rebated meeting stiles of a pair.

 
P
 
Pair door-set – Double doors supplied/tested as one assembly; may be rebated or square meeting stiles. (calc)

Panic device – A bar/rail across the door that releases latches for escape (EN 1125).

Packers (frame) – See Installation packers/shims.

 
R
 
Rebate (frame) – The step in the frame that the leaf closes against.

Rebated meeting stile – Overlapping edge on a pair to improve closing and sealing.

Reveal – The visible return of the wall opening; used when measuring structural openings.

 
S
 
Sash lock (DIN) – Combined latch + deadbolt; usually 72 mm centres; the everyday “workhorse” lock. (guide)

Seal (smoke / fire / acoustic) – Perimeter seals specified on the certificate; smoke seals are often brush; fire seals intumescent.

Self-closing device – Requirement for fire doors: a closer that closes the leaf from any angle.

Single door-set – One leaf and its frame supplied/tested together. (calc)

Smoke control door – Doorset tested/classified for smoke leakage (EN 1634-3). 

Stop (door stop) – The raised part of the frame the door closes against.

Structural opening (SO) – The masonry/timber stud opening into which the frame is fitted; basis for your calculator inputs. (calc)

 
T
 
Threshold – The strip or floor detail at the bottom of the doorway; can include a seal; mind accessibility rules.

Through-bolting – Bolting hardware through the door with sex bolts for strength (often required on closers/panic gear).

Tolerance – Allowed variation from the stated dimension; critical for frame gaps, leaf size and hardware preps.

Top/bottom rails – The horizontal members of the door leaf.

 
U
 
UKCA marking – Post-Brexit UK conformity mark that is replacing CE in GB for some products/hardware.

 
V
 
Vision panel – A glazed aperture in the leaf; must use approved fire-resisting glazing systems as per certificate.

Viewer (door viewer) – Peephole for visual identification.

 
W
 
Wall plug anchors / frame fixings – Approved fixings that secure frames to substrates.

Weather seal – Perimeter seal for external doors to limit wind/water ingress (separate from smoke/fire seals).
 
 
 
 
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