Makibishi

Makibishi are the Japanese version of the caltrop, small spiked devices with six or eight points used in feudal Japan to slow pursuers and defend fortifications. They were made in two main forms, iron tetsubishi and natural tennenbishi fashioned from the dried seed pods of the water caltrop, and their shape let them penetrate the straw waraji sandals commonly worn at the time. Beyond being scattered on the ground, makibishi could be thrown like shuriken, and ninja are recorded as sharpening their points and sometimes poisoning them; fighters commonly carried them in a belt pouch alongside other easily concealed weapons such as shuriken and grappling hooks.