FITTING A REPLACEMENT LOCK
Spare parts are available for many locks, so don’t rush into this job.
Before learn how to fit a replacement lock, examine the existing lock. Make a note of the manufacturers name and the model number as well as the size of main components such as the cylinder barrel or lock body.
Most manufacturers make replacement parts for both nightlatch and mortise locks, so if only the locking mechanism is at fault, it should be possible to replace this part alone rather than going to the expense of buying the entire lock plus all the fittings. For a nightlatch, you can buy a replacement cylinder
(with a new set of keys). For a mortise deadlock, replacement levers (with new keys) are available. These simply take the place of the existing levers inside the body of the lock. (A reliable locksmith will replace the levers for you, if you are unable to do it yourself).
If the lock is damaged beyond repair, you will have to buy a new one. But try if you can to choose a replacement that is the same size or slightly smaller than the original. This will save you a great deal of time spent in filling and patching, and you may be able to use some of the original parts — such as the striker plate.