The ShurLok offers a superior key storage solution to other products on the market. The ShurLok`s patented dual function on one set of dials allows one combination to be used for the key compartment (which you give to others) and another combination be used for the shackle. Shurlok is designed with an all-metal key storage lock box. Separate combinations open the shackle and key compartment -- combinations can be changed in seconds. All Metal construction - no plastic buttons or dials exposed to climate conditions. Zero locking - easily unlock the Shurlok, even in total darkness. With the zero lock feature, you can set the dials to all zeros and then count your numbers up to your combination on each dial.