Armour put on vehicles is usually made of metal and can include one layer over another with open spaces in between (spaced armour) or multiple layers of metal; ceramics (baked clay), and other materials. Another type of armour uses blocks of explosive that explode when another explosion goes off near it. This explosive armour protects by pushing against the other explosion. Vehicle armor is often angled to increase the amount of armour that must be shot through to get inside and to make the shot bounce off rather than piercing the armour.