Marks Key Below Security Doors Locks

Removing Marks mortise cylinder that screws into door lock: After you loosen set screws on faceplate, the cylinder can be unscrewed with... 
1. A key that fits into the cylinder, that does not work with the lock. (New key on old cylinder or Old key on new cylinder)
2. Putting key 1/2 way into cylinder and turning. 
3. A slotted screwdriver. 


IMPORTANT NOTES: The threaded cylinder has a groove down the side that the set screw fits into. The screw has to be removed enough for the cylinder to turn. When reinstalling, the screw has to fit back into the groove to hold the cylinder in place. Pay close attention to the cylinder before removal. The new one screws in the mortise lock and the orientation needs to be the same on the replacement. If the old lock has the cuts of the key pointing up or down-the replacement must be the same for the lock to work properly.