Rekeying is changing a lock so that a different key may operate it. Rekeying is done when a lock owner may be concerned that unauthorized people have keys to the lock. The lock may be altered by a locksmith so that only new keys will work. Rekeying is the relatively simple process of changing the tumbler or wafer configuration of the lock so a new key will function while the old one will not. Rekeying is done without replacement of the entire lock. Rekeying was first invented in 1836 by Solomon Andrews, a New Jersey locksmith. His lock had adjustable tumblers and keys, allowing the owner to rekey it at any time. Later in the 1850s, inventors Andrews and Newell patented removable tumblers which could be taken apart and scrambled. The keys had bits that were interchangeable, matching varying tumbler configurations. This arrangement later became the basis for combination locks.