Oval head phillips drive self tapping screws made of stainless steel. Sometimes called sheet metal screws or self tappers, these fasteners are common for home repairs as well as installing hardware on your boat. Oval head screws are used primarily for trim work or anywhere a smooth top is desired. The slightly rounded head projects above the finished surface and prevents the snags that occur when a flat head screw is not fully countersunk. Use where appearance is a factor.