A pipe bomb is a crude type of improvised explosive device used by terrorists and criminals, consisting of a metal pipe with two endcaps filled with some sort of explosives, often black powder or ammonium nitrate, with some kind of fusing mechanism attached. The device is typically targeted at a human target, as opposed to a building or vehicle, either as an improvised hand grenade or as a component to a mail bomb. Nails or other loose objects may be added to act as shrapnel.