An anvil devil is a small, triangular piece of hardened tool steel used by farriers and blacksmiths for cutting, marking, or creating V-notches in hot or cold metal bar stock. It acts as a portable, disposable cutting edge placed directly on the anvil face, often with three usable sides.

Key Features & Uses
Purpose: Primarily used for cold cutting or scarring steel to break it.
Design: Triangular, hardened steel bar (often 3.5" long) providing three cutting edges.
Versatility: Portable and small enough to be kept in a pocket.