Lumpy protrusions on the edges, and sometimes the underside, of a thunderstorm anvil.

a small metal weapon, worn over the knuckles on the back of the hand; called also brass knuckles and knuckle duster.

is any instrument consisting of finger rings or guards made of a hard substance and designed or adapted for inflicting serious bodily injury or death by striking a person with a fist enclosed in the knuckles.