A kunai (苦無 kunai) is a Japanese tool from the Sengoku period.
Originally used as an agricultural implement, a kunai in the right hands could become a multifunctional weapon, and due to its widespread use as such is strongly associated in popular culture with ninjutsu and its adherents.
There are two main variations, the short kunai ( 少 苦 无 shō-kunai) and the large kunai ( 大 苦 无 dai-kunai), which can differ in size from 20 to 60 cm.
The blade is triangular in shape, and at the end of the handle is a ring designed for tying a rope. The side edges are not sharpened, as the use of the tool as a shovel or chisel would damage the bevel.
The kunai was used in a wide range of trades in feudal Japan, especially gardening, carpentry, carving of various materials and even masonry, and was used for punching, carving, cutting, cutting, digging and any activity that required an iron blade, in the same way as the modern hori hori.
It was cheap and easy to produce, which facilitated its use in any field.
The sharp point of the kunai made it a perfect weapon for stabbing, and the ring on its handle helped to tie it to a pole as a spear or to a rope for use as a dart. Contrary to popular belief, the kunai was not intended to be a throwing weapon, but it could be used in this way with some efficiency thanks to its symmetrical design and balanced center of gravity.
There were also variants of kunai with blades of various sizes, with more than one blade or even with a serrated edge, similar to another tool called shikoro.
In addition to its other warlike uses, the kunai was used by warriors as a climbing piton, a harpoon or anchor for climbing walls and other obstacles, as well as an awl to open holes in walls or force doors.
It used to be said that the only impediment to using the kunai was the imagination of the wielder.
The kunai was used much more frequently than the shuriken in a ninja's arsenal, as it was comparatively more affordable, unobtrusive, versatile and easy to use.
Its status as a popular tool allowed it to pass without arousing suspicion should the bearer be searched or discovered in the midst of a mission.
The kunai is often depicted in manga, anime and video games as a common weapon of ninjas.