Doors have protective devices installed on them to make sure that you are safe while inside, and at the same time your home is safe while you are out. The most common ones just rely on locked door knobs that can be opened with a key. However, this is more prone to being broken in. With a more theft-proof item like supra lock boxes, you do not need a tangible thing that can be duplicated by use of tools even by criminals. Just choose a code that will serve as your password to entry, and anyone coming home do not have suffer being locked out without a key.