Do Safecrackers use Stethoscopes?

50 years ago, locks might have made enough noise for safecrackers to listen their way through a job, but modern locks are designed different.

“Do I wear a stethoscope to safe jobs?  Sure, but it’s only a showpiece,” says Marty Arnold of the Greater Philadelphia Locksmiths Association.  ”People expect to see one.”

Arnold tells UL.com that the key to opening a safe without the combination is in the hands, not the ears.

“Today’s locks don’t make the right noise in the right places, or are designed to make so much noise you can’t tell when you get the right combination,” says Frank Mullozzi, a member of the UL safecracking team.

As UL explains, most safes use combination locks with one- to four-number combinations.  Combination numbers correspond to wheels, or tumblers, in the lock.  Each tumbler has an opening or a gate.  When combination numbers are dialed in the proper directions, the gates line up and the lock will open.  

To bypass these safeguards, you need to know how many tumblers there are in the combination lock. This is tough, since the only ways to find out are by listening for the tumblers to touch each other when the dial is spun, or by drilling a hole through the door and using a scope to view them.

After the number of tumblers is determined, those educated in the art of lock manipulation can narrow down the dialing sequence and crack the combination – that is if they have enough time!