Your locks should be changed whenever you move into a new home, office or any time you suspect someone you don’t know/trust may have access to your home.
Unlike a forcible break-in, someone with a copy of your key can come and go undetected until you either notice missing items or, worse, discover and confront them in your home.
One way to change your locks is to have them re-keyed—changing the inside pinning so the old key no longer works and a new, differently cut key will work. Another way is to replace the locks entirely so the key for the old locks won’t fit in the keyhole.
There are options for upgrading the security level of your existing locks and brands and security levels can vary. Tell your locksmith what you want to achieve and ask for your options.