What Is A Mortise Lock?

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mortise lockset

Mortise locks are a specific type of lock set which are used in the commercial security industry and is used in applications which require a lock which is both heavy duty and high frequency.

The typical mortise lock is significantly different than your average cylindrical lock, which has the cylinder installed in the lever, with the latch bolt connecting to the chassis. 

The mortise lock also differs from a so-called “unit lock”, or otherwise known as a pre-assembled lock, which simply comes out of the box and is then inserted in a pre-cut area in the door for that lock.

Here is a quick video that illustrates exactly what a mortise lock is.  

A mortise lock is distinguished by the fact that it is made up of many different components, including the mortise lock body, as well as escutcheon trim plates (or rose plates) that fit perfectly on both the inside and outside of the door. 

mortise lock

It also comes with both inside and outside levers. 

All of these components assemble in a specific way, where the levers are connected through a spindle and onto the door itself via the mortise lock casing, as well as another separate cylinder.

Unlike a standard cylindrical lock, each of these pieces are completely disassembled to start with, and they must be assembled in your door the exact right way, using standard fasteners that come with the mortise lock, which the manufacturer supplies. 

Also included with your mortise lock should be a strike plate.

Once you have successfully installed your mortise lock set into your door, this strike plate is then installed onto the jam, which will allow the latch bolt to simply engage properly into that strike.

You will notice on your mortise lock set that the parts that come with it are much more heavy duty and visibly larger than other locks you may have had experience with before. 

This is due to the type of applications which mortise locks are meant for – commercial purposes which call for locks which can handle frequent use.

mortise lock

Included on the mortise lock are the hubs which the spindle will pass through, which are spring-loaded to power your lever, preventing it from sagging down. 

We also have the latch bolt, as well as the auxiliary locking latch.  In addition, depending on your application, you may also have a deadbolt as well.

If you install your mortise lock into a pre-assembled door, which is prepared to house your mortise lock, you will notice that the lock itself engages into this pre-existing cavity, fitting perfectly into that space. 

After the lock has been installed neatly inside the door, its time to install the escutcheons, or the outside trim, which will either be an escutcheon or rose type of trim.

mortise lock

If your mortise lock has an escutcheon trim, the door must be prepped for that type of plate to install on it. 

It also has a place for the cylinder to be installed through, with an inside plate which fits perfectly on to the inside of the door.

Once everything has been installed, with the cylinder screwed right into the mortise lock set, at this point you will be able to fasten the lock and secure it into place. 

After this step has been completed, its time to install the final piece, which is called the face plate or scalp. 

This is used to simply cover over all of the fasteners and screws which have been used to install the mortise lock.


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