Glossary - B

backcheck (n)
buffering feature within a door closing device to prevent a door leaf from being flung wide open (see also EN 1154)

backflap hinge (np)
butt hinge with extra wide flaps to spread load over a large area

backplate (n)
separate component on back of product providing the fixing means, and (where applicable) the bearing(s) for rotating spindle(s) etc. (see also EN 1906)

backset (n)
distance from the outer face of the forend (or faceplate if fitted) to the centre-line of the keyhole and/or follower

ball catch / ball detent (np)
catch containing a spring-loaded ball, the partial engagement of which in a recess in an adjacent component, resists the displacement of one component with respect to the other

bar ¹ (n)
(see "panic bar")

bar ² (n)
area between the pockets of a lever that is cut through by the gating

barrel ¹ (of cylinder) (n)
(see "plug")

barrel ² (of thrower) (n)
cylindrical part of a thrower into which the key pin is inserted

barrel and curtain (np)
thrower comprising a disc (curtain) to restrict access to the levers via the keyhole, and thereby prevent certain forms of picking attack

barrel bolt (np)
surface-mounted bolt², with shoot² of round cross-section, running in a continuous guide with slots cut in to locate the operating knob of the shoot² in both thrown and withdrawn positions

baseplate (n)
(Product specific term - see EN 1906)

bathroom lock (np)
privacy lock with latch bolt operated by lever handle or knob from both sides, and an additional deadbolt operated by thumb slide, thumb turn etc. from inside only (see also EN 12209)

bell crank (np)
pivoting component for changing the direction of linear movement, with or without magnification

belly / belly form (n/np)
edge of a lever where the key makes contact

belly relief (np)
reduction in the thickness of a lever in the region of the belly to reduce the risk of lateral pick up

bevelled bolt / chamfered bolt (np)
bolt with angled and/or curved surface on one side to enable it self-engage with the locking plate as the door closes

Birmingham bar (np)
steel bar fitted down hinge side of door frame to provide additional support for hinge fixings when subject to force attack

bit (n)
(see "key bit")

bitting (n)
process of cutting steps or notches into a key blank

blade (of key) (n)
that part of a cylinder key that is inserted into the plug

blank (of key) (n)
key without steps

bogey (n)
(Product specific term - see CEN/TS 13126)

bolt ¹ (part of lock or latch) (n)
moving part of a lock or latch that provides engagement between leaf and frame (see also EN 12209 & WI 33/250)

bolt ² (complete product) (n)
device for securing, or helping to secure, an opening leaf in the closed position, where movement of the engaging member (shoot) is effected from one side only, either directly by hand (thumb slide, etc), or via a lever, knob or non-differ key mechanism. (see also EN 12051 & prEN 14648)

bolt gauge (of rim locks) (np)
distance from the mounting surface on the door leaf to the opening direction side of the bolt head

bolt head (np)
outer end of the bolt¹ a part of which projects from the lock/latch and engages the locking plate (see also EN 179 and EN 1125)

bolt receiver (np)
component which engages the shoot ² of the bolt ²

bolt shoot (np)
(see "shoot ²")

bolt socket (np)
bolt receiver adapted for use in a hole in the frame or floor

bolt step (np)
step on the key bit of a lever lock that engages directly with the talon-form in the bolt tail, to throw and withdraw the bolt¹

bolt stump / talon (np/n)
part of the bolt¹ that locates in the pockets of the levers, and which passes through the gatings when correctly positioned

bolt tail / bolt lath (np)
thin part of the bolt¹ extending inside the lock case

bolt-through fixing (np)
method of attachment whereby the fixing means pass right through the door, window etc

bored latchset (np)
tubular latch, complete with associated (knob-type) door furniture, spindle and fixings (see also EN 12209)

bored lockset (np)
bored latchset in which at least one knob is lockable, and the key mechanism is contained within the knob. The latch may also have an anti-thrust bolt. (see also EN 12209)

bottom guide (np)
fitting at the bottom of a sliding or folding door leaf which engages the bottom guide channel (see also EN 1527)

bottom guide channel (np)
channel at the bottom of a sliding or folding door which guides the door leaf (see also EN 1527)

bottom pin / pin (np/n)
pin of a cylinder mechanism that is located in the plug and makes contact with the key

bottom pivot (np)
(Product specific term - see EN 1527)

bottom pivot socket (np)
(Product specific term - see EN 1527)

bottom rail (np)
rail at the bottom of a sliding door which supports the weight of the door leaf (see also EN 1527)

bottom rail sensor (np)
(Product specific term - see prEN 12650)

bottom roller (np)
roller at the bottom of a sliding door (see also EN 1527)

bottom rolling (adj)
having the weight carried on rollers running on a bottom rail set in the floor

bow (of key) (n)
enlarged portion of key at end remote from blade/bit

bow handle (np)
bow-shaped pull handle, fixed at both ends

bow latch (np)
latch with pivoting bolt attached to the follower

box striker (np)
locking plate with rigid enclosure behind one or more bolt aperture(s)

Bramah lock (np)
lock in which the movement of the detainers to their unlocked positions is by the axial movement of the key

break-glass bolt (np)
spring-loaded bolt held in locked position until glass (or similar brittle material) tube or panel is broken

break-out (n)
(Product specific term - see prEN 12650)

bridge ward (np)
ward where the obstruction is in the centre of the lock case

budget lock (np)
lock with swing bolt operated directly by a square key

bullet (of key) (n)
groove running the length of a key bit

bulleting (n)
arrangement of grooves and/or ridges running along the length of a key bit

burglar (n)
One who enters a building to commit a crime

burglar bars (np)
steel bars cut to length and fixed internally to window frames. Alternatively, securely fixed welded steel frames on the outside of windows

burglar resistance (np)
ability to resist forced entry

burglar resistant (adj)
comprising features to help prevent forced entry

burr (n)
plug which closes off the outer end of an individual pin chamber in a cylinder housing

burr strip (np)
length of material which closes off all the pin chambers in a cylinder housing

bush (n) (of lock)
component providing an enlarged and/or improved material bearing around the follower or key pin hole of a lever lock

butt hinge / butt (np/n)
single axis hinge with two flaps and a common hinge pin

Butter's system (np)
lock mechanism in which the bolt stump is replaced by a dummy stump which is moved by the bolt but starts and finishes in the same place

button (n)
catch in the form of a rotating element attached to one member and overlapping the other