SAFESHow a safe combination lock works

The mechanical dial lock

Behind the dial is a stack of round wheels, called a wheel pack, with one notch, called a gate, cut into each wheel. A bar called the fence sits over the wheels, on the end of a lever. When you dial the combination, turning the right number of times in each direction, you leave each wheel parked in turn with its gate lined up under the fence.

When the gates are lined up, the fence can drop into them. On most dial locks you then turn the dial a little further and the dial itself pulls the lock's bolt back, which frees the handle. On some smaller safes the handle does that job instead. Until the gates line up, the wheels keep the fence from dropping and the bolt can't move.

The electronic keypad lock

A keypad safe has a keypad on the outside and a lock body inside the door, joined by a cable. On most safe locks the electronics that check the code are in the lock body, not in the keypad. When you enter the right code, a small motor or solenoid moves a blocker out of the way of the bolt. The keypad is the easy part. The lock behind it is where it gets interesting, and the bolt work is mostly mechanical even on the electronic ones.

If your safe won't open

• On a keypad safe, change the batteries first, using fresh ones of the type the safe calls for. Weak batteries are a common cause.
• Check for a lockout. Many keypad locks stop accepting codes for a while after several wrong tries.
• Look for a backup key or external power contacts. Many keypad safes have one or the other, and the owner's manual will show where.
• On a dial lock, go slowly and follow the dialing instructions for your lock. The number of turns matters as much as the direction. Stop exactly on each number, and if you go past one, start over from the beginning instead of backing up.
• Don't force the handle. Pulling hard against a blocked bolt can make the problem worse.

If you've forgotten the combination

Look for where you wrote it down, and check the paperwork that came with the safe. Some manufacturers keep the original combination on file and can help if you can show the safe is yours. That only works if the combination was never changed. If that doesn't work, a safe technician can usually get it open. Sometimes that is done with no damage at all, and sometimes it takes a small drilled hole that is repaired afterward. A reputable one will ask you to show that the safe is yours.

Opening a mechanical dial lock without the combination, by feel and by reading small changes on the dial, is called manipulation. It's a skill that takes practice.