In steelmaking, a ladle was a large vessel of steel and cast iron framing lined with fire brick. In the first method for mass-producing steel, newly cast pig iron from the open-hearth furnace was poured into the ladle. A two-inch tap hole in the bottom was sealed with a clay plug to keep the steel from leaking out. When the steel was ready to be shaped into usable forms, workers removed the plug with a crook-shaped tool lowered over the side, and the molten steel flowed through the hole into molds below. Beginning in the 1970s, the steel flowed into a continuous casting machine rather than individual molds. This ladle could hold 10 tons of molten steel. The molds were empty cast-iron shells 18 inches by 20 inches by 72 inches. After they were filled and cooled slightly, an engine hauled them to a stripper building, where a machine lifted off the mold and left a block of steel called an ingot. The ingots were then taken to the mills to be shaped into various steel products.