The metal pot was kept filled by the operator tossing in small ingots of type metal every few lines, or later, by mechanical feeders that carry large ingots of type metal (and which often carried two ‘pigs’ at a time to be consumed in turn, the operator hanging a fresh one when one was consumed). These feeders are actuated by various methods, but the end result is the same: the ingots are fed little by little into the pot, keeping it filled to the correct level.