Iron anti-tank spike or caltrop (also known as caltrap, galtrop, cheval trap, galthrap, galtrap, calthrop, jackrock or crow's foot) which is an antipersonnel weapon made up of two or more sharp nails or spines arranged in such a manner that one of them always points upward from a stable base (for example, a tetrahedron). Caltrops were part of defences that served to slow the advance of horses, war elephants, and human troops. They were particularly effective against the soft feet of camels. In more modern times, caltrops are still effective when used against wheeled vehicles with pneumatic tyres. Caltrops were used extensively during WWI and WWII, and are still in use today used by special forces and law enforcement bodies.