Kunai

[Dianne]

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 [ninjutsus] 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.