A variety of grooves, slots, and pockets in the work-piece may be produced from a variety of tool bits. Common tool bit types are: square end cutters, ball end cutters, t-slot cutters, and shell mills. Square end cutters can mill square slots, pockets, and edges. Ball end cutters mill radiused slots or fillets. T-slot cutters mill exactly that: T-shaped slots. Shell end cutters are used for large flat surfaces and for angle cuts. There are variations of these tool types as well.