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

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