Never heard of “glass relockers”? That’s okay. Most people haven’t. Relockers are a category of devices intended to block a burglary of a safe. As their name implies, they relock a safe after the primary lock is cracked.

A glass relocker is based on burying a piece of tempered glass within the walls of a safe. It is attached, usually randomly, to one or more spring-loaded bolts. When a burglar tries to penetrate the layer where the glass is located, it shatters and the locking bolts spring into place.

This may not seem like a terribly sophisticated use of tempered glass, but it is to many government agencies who are concerned about security systems, and it is no accident that glass scientists in federal labs continue to study how to develop better and better glass relockers.

This video shows the efforts of the Discovery Channel’s MythBusters team to bypass a safe protected by glass relockers.