How does one way bulletproof glass work?

Question

How does one way bulletproof glass work?

In: 541

Answer 1

First Google result for “one way bullet proof glass” seems to do a decent job explaining it.

Basically using different layers of material they can make a bullet have a harder time moving in one direction than the other. Hard exterior layer that expands the bullet the softer layers to absorb energy. When shot the other way the still pointy bullet does not get slowed by the softer layer and carries its energy to the hard layer where it breaks through and keeps going.