A mortice lock is a lock that requires a pocket (or a mortice) to be cut into the door or piece of furniture into which the lock is to be fitted. Mortice locks may also include a non-locking sprung latch operated by a door handle. Such a lock is typically 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.
Mortice 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.
Installing a Mortice Lock
The installation of a mortice lock cannot generally be undertaken by the average homeowner since it is labor-intensive and requires 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.
Although the installation of a mortice lock actually weakens the structure of the typical timber door, it is stronger and more versatile than a bored cylindrical lock, both in external trim, and functionality. Whereas the latter mechanism lacks the architecture required for ornate and solid-cast knobs and levers, the mortice lock can accommodate a heavier return spring and a more solid internal mechanism, making its use possible. Furthermore, a mortice lock typically accepts a wide range of other manufacturers’ cylinders and accessories, allowing architectural conformity with lock hardware already on site.