The most common method of perforating metal uses a rotary pinned perforation roller. This is a large cylinder with sharp, pointed needles on the outside to punch holes into the metal. As the sheet metal is run across the perforation roller, it rotates, continuously punching holes in the passing sheet. The needles on the roller, which can produce a wide variety of hole sizes, are sometimes heated to simultaneously melt the metal which forms a reinforced ring around the perforation.