Similar to a trowel, the kunai is a wrought iron multi-purpose
tool originating in the Tensho Era of Japan (1573 - 1592). The kunai blade was unsharpened, soft iron, and was used for digging, prying, and smashing wood, plaster, and the like -- which would like have destroyed a
tool which was sharpened or heat-treated.
While generally a
leaf shaped blade atop a handle with a ring at the end, the kunai come in a number of different varieties, including
short,
long, narrow, wide, and saw-toothed. Due to the nature of ninjutsu'
s training with improvised and unusual weapons, the kunai became popularly associated with ninja (shinobi no mono), who might have used it as a weapon in disguise.