Wood screws are used in construction and woodworking projects.  Flat head wood screws are beveled under the head to fit into countersunk holes to create a flush finish against the wood.  Pilot holes can be drilled with slightly smaller diameters than the screw diameter to prevent splitting of the wood.  Length of the screw is measured under the head for pan head and hex head wood screws.  Flat head and oval head wood screws are measured from the top of the screw for length measurements.