Three-wheel combination locks use a single dial which must be rotated left and right in a certain combination in order to open the lock. Rotary combination locks are used on a verity of safes & vaults.

Within the locks are three mechanism discs, with notches that must be aligned to allow the lock to open. When entering the set code, you would start by turning the wheel to the set numbers set in the lock – The process is completed back and forth until all discs are in place, and the lock is released.