(also known as caltrop, galtrop, cheval trap, galthrap, galtrap, calthrop, crow's foot) is an antipersonnel weaopn 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). They may be thought of as the landmines of antiquity, useful to shape the battlefield and force the enemy into certain paths and approaches, or to provide a passive defense as part of a defensive works system. Tetsu-bishi served to slow down the advance of enimies.
The modern name "caltrop" is derived from the Latin calcitrapa (foot-trap). The synonymous Latin word tribulus gave rise to the modern Latin name of a plant offering similar hazards to sandaled or bare feet, Tribulus terrestris, whose spiked seed case can also injure feet and puncture tires. This plant can also be compared to the starthistle Centaurea calcitrapa , which is sometimes called the "caltrop". A water plant with similarly-shaped spiked seeds is called the "water caltrop", Trapa natans.
Tetsu-bishi did have to be made of metal!
Metal Tetsu-bishi were sometimes heavy, inconvenient, and expensive. They could be madeof Water Chestnuts,sharped wood or bamboo.
When pursued by enemies, ninja would scatter makibishi on the ground. In ancient Japan, common footwear consisted of sandals made of straw, called zori, which offered relatively little protection against such hazards. Makibishi spines were often hooked, and occasionally grooved to allow for a light coat of poison, to increase the damage they dealt to those unfortunate enough to step on them and possibly result in death.
These modern Tetsu-bushi can easily puncture this heavy sole! (above)