A sagger was a clay mould in which pottery was placed prior to firing in a pottery kiln. The sagger-maker's job was a highly skilled one, and his assistant, the bottom-knocker, made the base of the sagger and fitted it into a metal ring before the entire sagger, complete with clay pottery, was placed for firing. Ths sagger protected the pottery from the smoke and direct heat of the kiln.
With the advent of modern technology, the old bottle kins have been replaced by electric ovens, and the critical skill of the sagger maker - juding the temperature at which the correct firing took place, has died out. The only place to see saggers, and sageer makers, assisted by their bottom-knockers, is the museums around Stoke-on-Trent, the heart of the Potteries.