Locksmith Dictionary A – D

• action The arrangements of live or latch bolts and their accessories in a lock or latch, and how they function.
• alike change More than one lock or latch which can be operated by the same key.
• all to pass Often referred to as “locks to pass” i.e. a number of locks which can be passed or keyed alike (opened by the same key).
• anti-thrust bolt A spring bolt, for a night latch particularly, which cannot be pushed back when it has shot out and fastened a door.
• anti-thrust plate An overlapping metal plate fitted to outward opening doors so as to prevent access to lock bolts.
• automatic deadlatch A deadlatch, the main bolt of which is automatically locked (or deadlocked) when the door is closed.

• backplate A plate on the inside of a door through which the cylinder connecting screws and tailpiece is passed.
• backset The horizontal distance from the edge of a door to the center of a lockset.
• bar (OF LEVER) The part between the pockets which is slotted to allow the bolt stump to pass through.
• barrel and curtain This is the full name of a security device fitted in some locks to turn and close the keyhole when the key or any other instruments inserted through the keyhole is turned.
• barrel bolt The common kind of door bolt having a round shoot running in a long continuous guide or strap attached to the backplate, the shoot being provided with a knob or the equivalent for operation by hand.
• barrel key A key with a bit projecting from a hollow cylindrical shaft.
• bathroom lock A lock with a springbolt operable on both sides by furniture, and a deadbolt operable from the inside only, usually by thumb turn.
• bi-lock A pin tumber cylinder lock consisting of two parallel rows of pin tumblers and two sidebars operated by a U shaped key.
• birmingham bar A steel bar fitted to the inside face of a door frame on the hinge side.
• bit key A key with a bit projecting from a solid cylindrical shaft. The bit has cuts to bypass the wards or operate levers in the correct lock.
• bit key lock A warded or lever lock that uses bit keys.
• bitting A cut, or series of cuts, on the bit or blade of a key.
• blade The portion of the key that is inserted into the lock.
• blank A key before any cuts have been made.
• bolt The part of a lock or latch which provides the fastening or engagement by protruding from the case or forend to engage in the staple, striking plate, link, shackle or other member.
• bolt head The portion of a bolt that protrudes beyond the case of forend of a lock.
• bolt hole The hole in a case, forend, plate or staple to guide and/or admit the bolt.
• bolt stump According to some authorities, this is the name of the part that upstands, usually rectangular in section, on a dead bolt or runner which passes through the slot or gating in the levers as the bolt moves.
• bow The handle of the key.
• burglar bars Steel bars, usually round or square in profile, cut to length and fixed internally to window frames.
• by-pass tool A device that neutralizes the security of a locking device, or its application hardware, often taking advantage of a design weakness.

• cabinet lock A generic term to include all locks of any type for use on pieces of furniture, such as cupboards, drawers, chests, boxes and the like.
• cam Usually a tongue fixed to the end of the plug of a cylinder lock or latch.
• cam lock A lock that has an attached cam that serves as the lock’s bolt. Cam locks are often used on cabinets, file cabinets and drawers.
• cap (of the lock) The removable cover to a lock mechanism.
• case The housing or body of a lock.
• casement door A hinged door or pair of doors almost wholly glazed; often called a French Window.
• casement window A window in which one or more lights are hinged to open.
• case ward Protrusions that stick out of the sides of the keyway to allow entry of only the correct type of key blank.
• chamber The holes in cylinder housings that house top pins (drivers) and springs.
• change index The point on a key changeable combination lock dial ring to which the old and new combinations must be dialed when changing the combination.
• change key The key that operates one lock in a masterkeyed system.
• change key locks These are locks which can be operated by any key chosen from a large number of different keys that have been made for the purpose. The selected key is the only one which will open the lock until a change is deliberately made.
• claw blot A type of deadbolt having pivoted claws which swing out sideways when the bolt is shot. Such locks are usually fixed to sliding doors.
• clutch headed screw Threaded screws suitable for wood or metal with a shaped head allowing clockwise action to fix but no anticlockwise action to remove.

• close shackle padlock A padlock, the body of which is built up so that the minimum amount of shackle is visible when locked. It offers improved security against forcing or use of bolt-croppers.
• code A series of numbers or digits on a key or lock that specifies or references the particular cuts of the key to operate a lock.
• collar The shoulder on the shank of a rim, mortice or bitted key, controlling the point at which the key comes to rest after being fully inserted into the lock. The collar is the datum point from which the key is measured.
• combination lock An abbreviation of name for a keyless combination lock.
• concealed fixing (of locks or latches) A strong backplate is screwed to the door, the lock case slides over it and is secured in position by two or more grub screws which are concealed whenever the door is closed. This is usually associated with security night-latches.
• control key A key used to remove the core from an interchangeable core cylinder.
• control shear line The shear line which allows operation of the control lug of an interchangeable core.
• control sleeve The part of an interchangeable core retaining device which surrounds the plug.
• cover The part of a lock or latch which covers the mechanism and is fixed, usually by screwing, to the case.
• cross-bore A hole drilled into the face of a door where a bored or interconnected lockset is to be installed.
• cross differ An error situation whereby change keys (servant keys) operate more than one lock when this was not intended.
• cross rail The horizontal member of a door.
• curtain An abbreviation for barrel and curtain.
• cut cabinet lock A cupboard or drawer lock, the flange of which is recessed into the edge of the drawer or door.
• cuts A cut, or series of cuts, on the bit or blade of a key.
• cylinder Usually the cylinder with inner co-axial plug which houses the pins, top pins (drivers), or disc tumblers and springs in the cylinder body.
• cylinder housing With all component parts removed, this forms the main body or housing of a cylinder.
• cylinder key A key for use with pin tumbler and wafer tumbler cylinder locks.
• cylinder lock or latch Any lock or latch, the mechanism of which is contained in a cylinder.
• cylindrical lockset A bored lockset whose latch or bolt locking mechanism is contained in the portion installed through the cross-bore.
• cylinder rose (or ring) A shaped metal disc which surrounds the outer face of the cylinder of a cylinder mechanism assembly. It usually stands slightly proud of the outside face of door.

• deadbolt A lock bolt, usually rectangular, that has no spring action, and that becomes locked against end pressure when fully projected.
• deadlatch A lock with a beveled latch bolt that can be automatically or manually locked against end pressure when projected.
• deadlock A lock having only a square-ended deadbolt operable from one or both sides by key, and occasionally from outside only by key, inside by thumb turn. Sometimes operable only from outside and with no inside keyhole, which is designated a single-entry deadlock.
• deadlocking Pertaining to any feature which, when fully engaged, resists attempts to move the latch or bolt in the unlocking direction through direct pressure.
• deadlocking latch A latchbolt with a deadlocking mechanism.
• depth The depth of a cut is measured from the bottom of the blade up to the bottom of a cut. Depths are numbered starting with #0 (or sometimes #1) as the highest depth.
• depth key A special key that enables a locksmith to cut blanks made from a particular lock according to a key code.
• differs An abbreviation of “different combinations” or changes.
• disc tumbler lock A cylinder lock having disc instead of pin tumblers.
• door closer A device for closing a door or gate automatically after opening. There are numerous types available.
• door viewer Optical device fitted through a door to enable observation without opening the door.
• double-acting lever tumbler One which must be lifted a precise amount, neither too little nor too much to allow movement of a bolt.
• double-bitted key One with a bit on each side of the shank.
• double cylinder Pertaining to a lock with two keyed cylinders.
• double cylinder deadlock A deadbolt lock whose bolt may be operated by a key from either side.
• double feather spring Two separate feather springs, fitting closely together one inside the other. Alternatively both may be made form one length of material and remain joined at one end. A spring so made is more lively and likely to last longer than a single spring of thicker material.
• double locking 1. By introducing a different cam arrangement into the action of a cylinder rim nightlatch it is possible to give a double or deadlocking facility at no extra cost. A simple opposite turn of the key in the outside cylinder deadlocks both bolt and inside knob simultaneously. This gives protection against the bolt-forcing and the glass or wood panel breaking intruder. 2. Also where a lever lock shoots its bolt by more than one turn of the key, thus doubling the distance of its shoot.
• drilled-through spindle (for lock furniture) Usually shortened to DT. A spindle with a few holes drilled at each end, one of which accepts the screw passing through the neck of the knob (or lever handle) in the door furniture.
• drill-pin (sometimes pin) A fixed stump or pin in a lock onto which the hollow shank of a pipe key fits when inserted to operate the lock.
• drivers top pins. The pins in a lock that sit on top of the lower pins and rest against the springs.
• drop 1. In drawer, chest, box or similar cabinet locks, the vertical distance from the outside face of the top edge or selvage to the center of the keyhole. Sometimes this term is used for a keyhole cover an a padlock.