A kunai (苦無 kunai?) is a Japanese dagger, possibly derived from the masonry trowel. The two widely-recognized variations of the kunai are short kunai (小苦無 shō-kunai?) and the big kunai (大苦無 dai-kunai?). Although a basic tool, in the hands of a martial arts expert, the kunai could be used as a multi-functional weapon. The kunai is commonly associated with the ninja, who used it to gouge holes in walls. Kunai were originally made to be farming tools but soon evolved into the weaponry they have become today. Many popular manga and ninjutsu characters use kunai as both their primary and secondary weapons.
The kunai was conventionally wrought in lengths ranging from 20 cm to 60 cm, with the average at 40 cm. It was used by peasants as a multi-purpose gardening tool and by workers of stone and masonry. The kunai is akin to a crowbar. The blade is made of soft iron, and is left unsharpened because the edges are used to smash relatively soft materials such as plaster and wood, for digging holes and for prying. Normally, only the tip is sharpened.
Kunai normally had a leaf-shaped blade and a handle with a ring on the pommel for attaching a rope. The attached rope allows the kunai’s handle to be wrapped to function as a grip, or to be strapped to a stick as a makeshift spear; to be tied to the body for concealment; or to be used as an anchor or piton. Contrary to popular belief, kunai were not designed to be used primarily as throwing weapons. Instead, kunai were primarily tools and, when used as weapons, were stabbing and thrusting implements.
Varieties of kunai include short, long, narrow-bladed, saw-toothed, and wide-bladed. In some cases, the kunai and the shikoro, a wide-bladed saw with a dagger-type handle, are difficult to distinguish.