Forge Hearth of Mud Brick with a Clay Tuyere from the Back Wall

A forge is a hearth for heating metal: a bed of burning charcoal held against the mouth of a tuyere, the pipe that brings air from the bellows. The simplest is a hole in the ground with a pipe leading into it. Build a low box of mud brick with a clay pipe through the back wall, blown by bellows. The picture: a forge fire blown hot, throwing sparks.