A caltrop (/ˈkæl.tɹəp, ˈkal.-, ˈkɔːl.-/; also known as caltrap, galtrop, cheval trap, galthrap, galtrap, calthrop, jackrock or crow's foot) is an area denial weapon made up of usually four, but possibly 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)....
