Hole saws are cylindrical cups with a serrated edge to cut various sizes of holes in a variety of materials. The serrated edge is designed to cut the hole; the other end is designed to be driven by an arbor or drill chuck. There is a wide variety of hole saws available in the marketplace, from inexpensive carbon steel hole saws to extremely specialized, application driven hole saws. The most commonly used saw, however, is the bi-metal hole saw.