Ninja didn't like to fight direct with the enemy. Their primary purpose was spying, not killing enemy soldiers. So they were good at escaping. Makibishi or Tetsubishi was one of their escaping gear. A makibishi or Tetsubishi is a small spine to sting the sole of a foot. When a ninja is being chased by enemy soldiers, he scattered numerous makibishi or Tetsubishi to the ground. Because zori (Japanese shoes) were made of grass in those days, Tetsubishi or makibishi's spine could easily penetrate the shoes. The spine of a makibishi was often hooked, so it would be terribily painful if someone step on a makibishi. .Some ninja had a more flashy version of makibishi, which exploded when someone stepped on it, it was called Bakurai-bishi . The Tetsubishi was used to slow down pursuersor to protect doorways.
