The security of your antique lock depends on the type of lock it is as well as its condition. The first thing you should do is check to see if there is any obvious damage to the lock. Has it been gouged or dented? Look for scratches indicating that someone may have opened the lock case at some point and tampered with the lock. If it is a padlock, hold the shackle so that it can’t move and try shaking the lock. If it rattles, something is broken inside and your antique lock is not secure.
The next step is to check to make sure the lock operates properly when the key is inserted into the lock and turned. The key should turn smoothly and open the lock without any problem. It it is difficult to turn the key, the lock mechanism could be in danger of setting up. This does not make the lock less secure. However, if the lock sets up, you will not be able to open it either. An antique lock that is difficult to open can be treated with WD-40 to lubricate the mechanism. Sometimes this will free it up so that it operates as it should. If the mechanism is hard to turn, don’t try to force it. The extra pressure can cause your antique lock key to break off inside the lock.
Another thing you should do is to gently rap the padlock on the side of the case and then try pulling the shackle open without the key. This test will fail if the bolt spring is broken inside of the lock. If you determine that the lock is broken, you can contact a locksmith who does antique lock repair. There are still antique lock parts available for many old locks, and if the parts are not available, some locksmiths are able to recreate the parts that are needed.
Of course, just because your antique lock is in proper working order does not mean that it is totally secure. Security is an illusion; no matter how good your lock is, there is always someone who can get through if they have the right skills and tools. The level of security a lock provides is simply a measure of how difficult it would be to pick, bump, decode, or destroy the lock.
Some locks are quite easy to unlock without a key. Almost all modern pin tumbler locks, which are commonly used in homes and thought by most to be secure, can be bumped open in seconds by anyone who has the right tools. Warded locks and wafer locks are not very secure at all. Lever locks can’t be bumped but they can be picked. An antique lock box, also known as a rim lock, uses a skeleton key and is not very secure.
The most secure locks are disk locks and slider locks. Disk locks have an internal structure similar to that of a combination lock and most are very secure, but some can be decoded quite easily. Locks that use sliders instead of pin tumblers are extremely secure. If the security of your antique lock is important, make sure you are using a type of lock that is more difficult to pick or decode.