A dial on a mechanical combination lock for a safe is used to confirm the entered combination and open the safe. After the correct combination is set, the user typically turns the dial clockwise or counterclockwise, depending on the lock's configuration. This rotation activates the lock's internal mechanisms and unlocks the deadbolt, allowing the safe to be opened. The dial is therefore crucial to the actual opening process of the safe, ensuring the security of the items stored within by using a predetermined combination.