Many mortise Cylinder locks are installed with a trim plate on the door that has predrilled holes for the lock cylinder and door knob. Keep in mind that these are trim plates, not cylinder guards. These trim plates are hollow and can easily be dented in to allow the lock pulling tool a better bite on the cylinder.

These are similar to the above, but provide more security and are much more involved or complicated to install. It cannot be installed onto the door right away as a cylindrical lockset. Its installation is possible only when you router out the section of the door to create a pocket for the lock body. These mortise locks are quite popular in offices and high-end commercial buildings. Some renowned lock brands associated with these locks are Sargent