An anvil is a metalworking tool consisting of a large block of metal (usually forged or cast steel), with a flattened top surface, upon which another object is struck (or "worked"). Anvils are massive because the higher their inertia, the more efficiently they cause the energy of striking tools to be transferred to the work piece. In most cases the anvil is used as a forging tool. Before the advent of modern welding technology, it was the primary tool of metal workers. The great majority of modern anvils are made of cast steel that has been heat treated by either flame or electric induction.
https://en.wikipedia.org/wiki/Anvil