Types of head The two basic head shapes are round-head and countersunk and both are available with cross-head or slotted drives. Round-head screws are used mainly for holding thin materials which cannot take countersunk screws. This generally means fixing metal things to wood in positions where the shape and appearance of the head is hidden or docs not matter. With this head you need to drill only a clearance hole and a pilot hole. Countersunk screws are shaped so that their heads can be sunk into the surface of the top material you are fixing. They are less obtrusive than round-head screws and must be used where a bulky head cannot be tolerated such as fixing hinges. Besides needing to drill a clearance hole and a pilot hole, you may have to make a tapered hole for the head with a countersink bit particularly when fixing metal or hardwoods. With soft woods, tightening the screw to pull the head into the wood may be enough. A third type of screw, known as a raised countersunk, is ...