Door locks are an important part of your house's security system. Signs that you need to replace your locks include: Problems with inserting or turning the key in the lock cylinder; rough operation of the thumb latch on the inside of the door; and having the spring-loaded door bolt stick in one position or not operate smoothly. If a handle is loose or doesn't turn easily, it's also time for replacement. Stick with the quality brand names and make sure to get hardened deadbolts. It's also a really good idea to have all of your exterior door locks keyed alike.