If you have moved into a very old house and find that you have an old door that is locked, your first thought is probably, "That is weird. Maybe we should leave it locked". Your second thought will probably drift toward insatiable curiosity, and not having a key, you will need a locksmith's help to get the door unlocked. This is how a locksmith works his or her magic on a very old door that no longer has a key.

Removing the Hinges 

If the hinges on this old door are exposed on the outside of the door, the locksmith may just remove the door this way. Old doors often had (and still have) pin bolt hinges. When you pull the pin bolts up and out of the hinges, the hinges come apart and you are able to remove the door rather than try and pick the lock. Sometimes the hinges are painted and stuck fast or badly rusted or corroded. Some anti-rust lubricant spray can help release the pin bolts enough to hammer them up and out. A utility knife might scrape away enough paint to pull the bolts free, otherwise paint thinner will remove the paint and free up the bolts.

Picking the Lock

Old locks often require a skeleton key, but that complicates the modern lock picking process because of the way the internal tumblers in these locks worked. Without the key, picking this type of lock is exceedingly tricky, but not impossible. The locksmith has to manuever his lock picking tools about to get a good feel for how the tumblers are shaped and how they work before finally unlocking the door. Crafting a brand-new key for the old lock may just be the better option in some instances.

Making a New Key

If picking the lock does not work, and the door's hinges are on the inside of the door and unaccessible from where you stand, then making a brand new key for the old door is the only option the locksmith has left. If the lock requires a skeleton key, most skeleton keys have a bar across the top that, when inserted into the lock, either depressed a mechanical button or grabbed hold of a pin and hold fast until the key turns against the tumblers. Your locksmith starts with this aspect, and then attempts to find a match using several common skeleton key forms, which he or she has stored in his or her supplies. 

Once the locksmith finds a skeleton key that works in your lock, or finds one that is a close match, he or she can do several mock-ups of keys that also seem to fit. One of these mock-ups will have the necessary missing component or "teeth" which will fit the door perfectly and unlock it. At this point, the locksmith will make you copies of the fake key that worked so you can lock and unlock this mysterious door from this point onwards.