T

two step progression
n. a progression using a two increment difference between bittings of a given position

tumbler
n. a movable obstruction of varying size and configuration in a lock or cylinder which makes direct contact with the key or another tumbler and prevents an incorrect key or torquing device from activating the lock or other mechanism

top pins
The pins in a lock that sit on top of the lower pins.

top master key
The highest level masterkey that fits all the locks in a multi-level masterkeyed system.

TMK
abb. top master key

tip stop
n. a type of stop located at or near the tip of the key

tip
n. the portion of the key which enters the keyway first

theoretical key changes
n. pl. the total possible number of different combinations available for a specific cylinder or lock mechanism

tang
The end of a file where a handle is to be attached.

tailpiece
n. an actuator attached to the rear of the cylinder, parallel to the plug, typically used on rim, key-in-knob or special purpose cylinders