Anvil

Anvil is an implement made of a heavy steel or iron block having a flat top, concave sides, and typically pointed end. Metals are placed on the flat top and hammered to give them a desired shape.

Anything of anvil-shaped is also called anvil, such as anvil in anatomy for incus having anvil-shaped bone, or anvil cloud for the horizontally extended upper part of cumulonimbus cloud.