Brass Knuckles, called Tekko (鉄甲, lit. "iron", "armor") were a fist-load weapon used by the samurai and shinobi. They were made out of wood or metal, and sometimes out of horseshoes by tying two horseshoes together directly facing and overlapping each other. Heavier varieties were effective against enemies wearing armor.
The horseshoe design provided greater hand mass, and defensive guard, but resulted in larger weapons, not easily concealed, and difficult to learn. An improved horseshoe tekko featured the two horseshoes welded together. However, the popularity of the horseshoe tekko faded, as attention turned to the smaller, more concealable horse stirrup.
The Tekko was sometimes enhanced by embedding additional bolts into the horseshoe shape, to inflict greater injury. Other styles of tekko exhibit sharp protrusions at either end and three spikes representative of the position of the knuckles.