Double hammer

A double hammer is a forging implement used in metallurgy. It operates on puddle balls and blooms by hitting both sides at the same time.^[1] Double hammers are made of two blocks attached to rollers which facilitate opposing movement along a set of rails.^[2] Double hammers are normally operated by three people at a time: one holding the instrument in place and the other two moving the blocks back and forth.^[3]