The circular saw is a metal isc or blade with saw teeth on the edge as well as the machine that causes the disk to spin. It is a tool for cutting wood or other materials and may be hand-held or table-mounted. While today they are almost exclusively powered by electricity, larger ones, such as those in "saw mills", were traditionally powered by water turning a large wheel. Most of these saws are designed to cut wood but may be equipped with blades designed to cut masonry, plastics or metal although there are purpose-made circular saws specially designed for particular materials.