The circular saw is a metal disc 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. It can also be used to make narrow slots. Most of these saws are designed to cut wood but may be equipped with blades designed to cut masonry, plastics or metal. There are also purpose-made circular saws specially designed for particular materials. While today circular saws are almost exclusively powered by electricity, larger ones, such as those in "saw mills", were traditionally powered by water turning a large wheel. [via wikipedia]