Do you know who has the keys to your home or business? If you have had the same keys for more years than you can remember, the answer is probably that you do not. Most keys can be easily duplicated (see Products for Non Duplicable Keys), and over time you have probably had more made than you remember.
Changing a lock cylinder (rekeying lock) so that new keys operate them is a simple procedure for a locksmith and it instantly gives you a specific answer to who has your keys. If you have too many different keys for different locks floating around, it is also possible to key those locks “alike”, or make other minor modifications (usually), so that you have fewer keys to keep track of and therefore a better idea of who has them.