Mortise lock

A mortise lock (mortice lock in British English) is a lock that requires a pocket—the mortise—to be cut into the door or piece of furniture into which the lock is to be fitted. In most parts of the world, mortise locks are found on older buildings constructed before the advent of bored cylindrical locks, but they have recently become more common in commercial and upmarket residential construction in the United States. They are widely used in domestic properties of all ages in Europe.

Mortise locks may include a non-locking sprung latch operated by a door handle. Such a lock is termed a sash lock. A simpler form without a handle or latch is termed a 'dead lock'. Dead locks are commonly used as a secure backup to a sprung non-deadlocking latch, usually a pin tumbler rim lock.

Mortise locks have historically, and still commonly do, use lever locks as a mechanism. Older locks may have used warded locks. This has led to a popular confusion between the two; the term 'mortice lock' is widely known and used, but usually in reference to lever keys. In recent years the Euro cylinder lock has become common, using a pin tumbler lock in a mortice housing.

The parts included in the typical US mortise lock installation are the lock body (the part installed inside the mortise cut-out in the door); the lock trim (which may be selected from any number of designs of doorknobs, levers, handle sets and pulls); a strike plate, or a box keep, which lines the hole in the frame into which the bolt fits; and the keyed cylinder which operates the locking/unlocking function of the lock body. However, in the United Kingdom, and most other countries, mortise locks on dwellings do not use cylinders, but have lever mechanisms.

The installation of a mortise lock can be undertaken by the average homeowner with a working knowledge of basic woodworking tools and methods. Many installation specialists use a mortising jig which makes precise cutting of the pocket a simple operation, but the subsequent installation of the external trim can still prove problematic if the installer is inexperienced.

...
Wikipedia