Automobiles use a large number of parts cast from molten metal. For instance, the engine block of a Model T was made of cast iron. To make a block casting, an iron molder would fill a large box with special molding sand and insert hard sand "cores" that represented voids inside the block, where the iron would not flow. The molding sand was rammed into the mold, around the cores, either by hand tools or with an air-powered rammer. Then molten iron was poured into the mold. When the iron cooled and solidified the sand was broken off and poured out, leaving behind the finished casting. Molding was originally a skilled job, but standardization and mechanization reduced it to a semi-skilled job.