Stonemasons build stone walls, as well as set stone exteriors and floors. They work with two types of stone—natural-cut stone, such as marble, granite, and limestone; and artificial stone, made from concrete, marble chips, or other masonry materials. Masons use a special hammer and chisel to cut stone. They cut stone along the grain to make various shapes and sizes, and valuable pieces are often cut with a saw that has a diamond blade. Stonemasons often work from a set of drawings in which each stone has been numbered for identification. Helpers may locate and carry these prenumbered stones to the masons. A derrick operator using a hoist may be needed to lift large stone pieces into place.