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Locked Door

What is a Mortise Lock?

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A mortise lock is a type of locking device comprised of a large, rectangular body that fits into a similarly shaped pocket or mortise which is carved into the edge of the door. The body of the lock houses the parts that actually work the lock, including workings for the knob or handle, latch, and deadbolt. When you look at the frame of a door with a mortise lock, you will see a solid metal plate that is flush with the frame and securely screwed in place. Within that plate is an opening, and the locking device on the door, usually a thick, steel bolt, slides into that opening (or mortise) when it is turned with a key. The result – a very secure doorway.

From a historical perspective, with the development of bored cylindrical locking devices, the mortise lock began to fall out of favor. The primary reason was the skill required to install it. For quite some time these locks were mostly found on older buildings, doors and furniture which were constructed prior to the advent of newly developed locks. However, since the lock itself is so strong, its security potential couldn’t be denied, and the use of the mortise lock is slowly returning in popularity in commercial structures and high end residential buildings.

A mortise lock consists of several parts:

1) The lock body is the part of the locking device that is actually housed within the mortise bored into the frame of the door.

2) The lock trim can consist of any number of designs of doorknobs, levers, handles or pulls which are actually used to open the door itself.

3) The strike plate lines the hole in the frame into which the bolt inserts when the lock is engaged and the door is locked.

4) The keyed cylinder is the tunnel housing the structures that operate the locking and unlocking function of the lock body.

Like any lock, there are pros and cons to mortise locks. The biggest drawback to a mortise lock is the skill needed to install it. Because the frame of the door must be carved out to accommodate the lock body, familiarity with woodworking and the tools of the trade are a must in order to achieve a solid fit. Yet experts have found that, while boring a hole in the frame tends to weaken the structure of the door, the lock itself is superior in strength to a typical bored cylindrical lock.

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