Understand when, why, and how to rekey a lock with this handy guide. What it Means to Rekey a Lock A pin and tumbler lock—the kind of lock found on locking doorknobs and deadbolts—contains a steel cutaway that holds a cylindrical plug and a number of springs and pins that allow a specific key shape to turn in the lock. In order for a key to turn the locking mechanism, the configuration of the pins must match the depth of the unique grooves on that key. When you want the lock to open with a different existing key—say, so you no longer want to use separate keys to enter the front, back, and side doors—the lock must be disassembled and the pins, which are of various heights, removed and replaced by new pins that match the cuts and grooves in the new key.