Glossary of Locksmith Terms

Thank you to the Lock Industry Standards and Training (LIST) Council for the following terms:

auxiliary spring

n. a secondary spring used to support the lever handles of a lockset

back plate

n. a thin piece of metal, usually with a concave portion, used with machine screws to fasten certain types of cylinders to a door

back check

n. the resistance provided by a door closer as a door is opened


n. the distance between the center of a cross-bore and the bolt edge of a door or drawer

ball bearing

n. 1. a metal ball used in the pin stack to accomplish some types of hotel or construction keying, 2. a ball, usually made of steel, used by some lock manufacturers as the bottom element in the pin stack in one or more pin chambers, 3. any metal ball used as a tumbler’s primary component, 4. used as a means of repairing a drilled hole in a safe when welded in place

ball bearing hard plate

n. a hard plate that contains metal balls, typically two types, imbedded in a honeycomb pattern, or free moving within a hard plate envelope

ball bearing hinge

n. a hinge which uses ball bearings between its knuckles to reduce friction

ball catch

n. a latch which uses spring pressure to force a ball bearing into a recess in its strike

ball check

n. a spring loaded ball bearing in a door closer arm assembly that acts to limit arm travel

barrel bolt

n. a surface mounted slide bolt which has a cylindrical shape

barrel key

n. a type of bit key with a hole drilled into the shank from the tip

barrier free

n. having to do with the absence of restrictions to access by the handicapped

Barron, Robert

the Englishman credited with the invention of the double-acting lever tumbler in 1778

bell box

n. the protective enclosure for a bell or other alarm sounding device

Bell type key

n. a key whose cuts are in the form of wavy grooves milled into the flat sides of the key blade. The grooves usually run the entire length of the blade.