A mortise lockset consists of two parts – the mortise lock body, and the box keep. The lock body is installed into the door, while the box keep is the part that is fitted into the door jamb.
The mortise lock takes its name from the fact that it requires a mortise – or a pocket – to be cut into the door or the object on which the lock is being fitted. Mortise locks are not new, they have been around for an incredibly long time, and were used extensively before bored cylindrical locks were invented. In fact, the mortise lockset has come back into fashion in recent years, and it is now quite common in residential homes in the USA.
The mortise lock is a dual action type of lock – it acts both as a doorknob and a deadbolt. Most modern locks are sash locks, which operate using a non-locking spring latch which can be opened using a door handle. Mechanisms that don’t have the latch or handle are called dead locks. These are usually used as an extra form of security, acting as a backup for a sprung non-deadlock latch, such as a pin tumbler lock.
It is common or mortise locks to use a lever lock as a mechanism. However in some older lock systems a warded lock was used instead. This phenomenon is often a source of confusion, as people associate the modern locking system with the word mortise. However, it is now more well-known that the euro cylinder lock, with a pin tumbler, can be found in traditional mortise housing.
The typical US version of the mortise lock includes a lock body and a trim, as well as a strike plate to protect the jamb, and a box keep.
Installing a Mortise Lock
In general, the installation of a mortise lock cannot be performed by an average person – it requires some specialist woodworking tools and an understanding of basic woodworking methods. Most people would be better off hiring a specialist that owns a mortising jig so that they can do a good job of installing the lock correctly.
Remember that a lock is only secure if it is properly installed. If the frame is weak or the lock does not shut securely then it would be easy to breach.
The installation of the mortise lock actually does weaken the structure of the door slightly, but it is still generally more versatile and stronger than a cylindrical lock, and this means that it is a better option for the average home and for most commercial properties too – as long as it is fitted by a professional. You can get mortise locks that look very similar to other styles of locks, ensuring that your property still has the period appearance or architectural conformity with neighbouring properties if that is something that is important to you or a condition of the tenancy in the area where you live.