The workpiece is placed into the forge. Then the impact of a hammer causes the heated material, which is very malleable, to conform to the shape of the die and die cavities. Typically only one die is needed to completely form the part. Extra space between the die faces causes some of the material to be pressed out of the sides, forming flash. This acts as a relief valve for the extreme pressure produced by the closing of the die halves and is later trimmed off of the finished part.