Do you know who has your home key? You just moved in and want to make sure you are the only one that can enter. Or a family member lost their key and they might have been followed home. Maybe you gave your key to a friend you no longer see or a neighbor. Then you don't have to change your door or lock, you simply have to change your cylinder. You can enhance the security of your home by changing your cylinder and you can be sure no one has the key.