Sheet metal notchers carve out rectangles, triangles, and other shapes along the edges of flat metal sheets. Their cutting blades or dies shear through workpieces to make clean cuts. Also known as corner notchers, they are commonly used to remove the corners of sheets and leave flaps that can be folded in to form trays, pans, and boxes. Manual notchers have a lever handle or foot pedal to drive their cutting blades. They typically notch lighter-gauge sheet metal than corded and air-powered models. Corded notchers cut heavier-gauge sheet metal with less effort than manual notchers. Air-powered notchers run on compressed air and contain few moving parts, so they typically run cool, have a long lifespan, and weigh less than corded notchers.