Locksmith-Dictionary M-P

master key A key which will open every lock in the master keyed suite.
master keyed (locks or latches) A lock or latch capable of being operated also by a master key as well as its own change or servant key.
master pins Small pins sometimes called wafers to build up chamber pin loading in pin tumbler master keyed cylinders.
mechanism (of locks or latches) The arrangement of the component parts and the manner in which they perform to achieve the required security and differing when operated by its key.
mortise A hole cut into the thickness of one edge of a door to receive a mortice lock or latch.
mortice lock (or latch) A lock or latch which is morticed to let into the thickness of the door from the meeting edge and held in position by screws through the forend.

narrow case lock or latch A rim lock or latch, the case of which is made specially narrow, usually less than three inches wide, for fixing to the narrow stile of a panelled or flush door.
nightlatch A rim or mortice latch with a bevelled springbolt or roller bolt which shoots when the door is closed, but can be withdrawn by key from outside and by knob or lever handle from inside.
nozzle A circular boss or ferrule containing the keyhole on some cabinet locks, including locker locks. Correctly relating to lever cabinet locks.

pan The removable mechanism chamber attached to the inside face of a safe door.
panel grilles Steel grilles made to size with various infills of expanded diamond mesh, square weldmesh or fancy infills, usually fitted internally.
peg ward A combination of wards resembling a sash ward but fixed by pegs to the lock case.
pins Usually the lower of each pair of tumblers in the pin tumbler cylinder mechanism. The upper are known as drivers.
pin stack The combination of a lower pin sitting beneath an upper pin. In master keyed locks, additional master pins may be located between the lower and upper pins.
pin tumbler mechanism The mechanism incorporated in the cylinder or body of a cylinder pin tumbler lock, latch or padlock.
pipe key A key with a flat bit and a hollow circular shank to locate on the drillpin. Used only on one-sided locks.
plug The part of the lock that you put the key into, and which turns to operate the lock.
pre-assembled lockset A lock designed to be installed into a cutout in the edge of a door. The lock body and most or all of its trim need no further assembly other than securing it to the door.