Makibishi

The term makibishi (撒き菱 or 撒菱) refers to the Japanese version of the caltrop.

Description
Makibishi (igadama), sharp spiked objects that were used in feudal Japan to slow down pursuers and also were used in the defense of samurai fortifications. Makibashi were one of the items supposedly used by ninja. Iron makibishi were called tetsubishi while the makibishi made from the dried seed pod of the water chestnut formed a natural type of makibashi called tennenbishi. Both types of makibishi could penetrate the thin soles of the shoes such as the waraji sandals that were commonly worn in feudal Japan when the makibashi was dropped on the ground or planted in advance. Makibishi could be carried in a bag attached to a belt along with other commonly carried weapons and/or tools such as shuriken and kaginawa. Makibashi could be thrown like a shuriken                    and could also be used against an enemy on horseback.