A saw is a tool made of a strong blade, wire, or chain with a hard jagged edge. It is used to cut materials, most often wood, although metal or stone is sometimes cut by placing a jagged edge on the material and moving it forward with less force. Usually with a serrated blade or disc. There are two types of electric circular saw, the infinite screw and the side screw. The helical saw has enough torque to cut wet wood and concrete.