If you give your keys to others, they can have copies made quickly and easily at one of millions of key cutting centers. Be sure to understand how easily this can happen and protected by a patent and carry the appropriate certifications. How often do you give your keys to other people? Consider the babysitter, the gardener, neighbors, friends, family, parking attendants and how easily they might duplicate a key for convenience and forget to tell you.
When searching for s truly secure lock, always look for locks that provide protection against drilling or picking, as well as those that have a long enough bolt so that the door cannot be pried open. Additionally, some locks have bolts that are made of hardened material or have hardened inserts to protect against a possible intruder from sawing the bolt.