Kunai is well known as well as shuriken (ninja throwing stars, multi-pointed throwing weapon) and makibishi (small, spiked caltrops used by ninja) as tools used by ninja, but kunai was little used except the case where it was needed immediately as a substitution because it was made of a high quality wrought iron.
忍者の使う道具としては手裏剣やまきびしと同様に良く知られているが、良質な鍛鉄で作られるためとっさの代用以外はあまり利用されなかった。