Lock and Key Mechanism Identification
Domain 2 tests classification of locks and keys by mechanism, keyway, and operation, using terms that another examiner can verify.
Mechanism families
- Pin tumbler: shell, bible, plug, key pins, driver pins, springs, shear line. The key lifts key pins so the break between key and driver pins aligns at the shear line. Found in cylindrical, mortise, rim, and key-in-knob cylinders.
- Wafer: flat wafers ride in slots and must align at the shear line; there are no driver pins. Common in cabinets, padlocks, and some automotive locks.
- Lever: levers with gates and a curtain or bolt stump; a bit key or lever key lifts levers to the gate height. Common in mortise and older padlocks.
- Disc detainer: rotating discs with gates and a side bar; tubular, axial, and some high-security keys operate them.
- Other families: dimple, magnetic, combination, push-button, and electronic or electromechanical locks.
Key features
Identify the keyway profile, warding, blade shape, shoulder, tip, and bow markings. Distinguish a key blank from a finished key and a master key from a change key. Record manufacturer or trademark only when legible.
Worked example
A key has a hollow, cylindrical blade with radial cuts and a round bow. That points to a tubular key, typically operating a disc-detainer or pin-tumbler tubular lock, not a standard flat pin-tumbler key. The conclusion changes the examination: look for disc gates and a side bar rather than pin chambers.
Traps
- Calling every small lock a 'wafer' or every cylinder a 'pin tumbler' without seeing the mechanism.
- Ignoring keyway and warding when matching a key to a lock.
- Confusing master-key hierarchy with a single key's cuts.
- Over-reading worn bow stamps as manufacturer proof.