A mortise lock body is a part installed in a door or piece of furniture

A mortise lock body is a part installed in a door or piece of furniture that houses the bolting mechanism. It also comprises a strike plate that lines and reinforces the hole in the facing frame into which the bolt shoots. There are several different types of mortise locks, but they all have the same basic function – to allow a key to operate the locking and unlocking functions within the lock.

A typical mortise lock has a handle or lever placed onto an ornate to modern escutcheon that is attached to the faceplate. The lever or knob pushes a follower, which pulls the latch to retract it. Once the latch is pulled, a cam on the lock cylinder rotates and the bolt is released. The mortise lock body is often fitted with a hard collar, which spins freely on the cylinder and prevents the use of a pipe wrench to pry it out of the doorway.

When replacing an existing mortise lock, the escutcheons and handle or lever need to match so the new mortise lock can be screwed into the existing door preparation. This can be difficult, especially if the old lock has an unusual finish. The best way to ensure a perfect match is to purchase a high pressure cast Zamac mortise lock body, which has the same dimensions and profile as the original, but can be used with any standard escutcheon.

In addition to the type of escutcheon and lock body, there are many other factors that should be taken into account when choosing a replacement for a mortise lock. The key hole location must be the same, and a measurement called the backset must be taken of the distance between the selvedge edge (where the bolt shoots through) and the keyhole pin in the furniture. Then, the mortise lock body must be sized to this measurement.

Once a suitable replacement has been found, the first step is to prepare the door for the new lock. This is not an easy job, and should be performed by a professional who has experience in working with mortise locks and the proper tools for this kind of work. A rectangular hole is required to be chiseled out in the door, so this is not something that most homeowners can do themselves.

The next step is to remove the existing levers or knobs, then loosen the two setscrews that secure the interior knob or lever on the interior side of the lock if they are equipped. Loosening these screws will enable the mortise cylinder and thumbturn to be removed, which will free up the latch bolt inside the door. The strike plate will then need to be removed by unscrewing it from the frame. The lock body can then be removed by unscrewing the edge mounting screws on its backside. Depending on the rust, this could take anywhere from 20 minutes to 2 hours. Once the rust is removed, the metal parts can be rinsed with water to clean them.