The steel self-drilling screw with zinc plating has an 82-degree flat head and a star drive. Steel is often used in applications where strength is the primary consideration. The zinc plating offers corrosion resistance and has a reflective appearance. The flat head has an 82-degree cone-shaped bearing surface for use in countersunk holes and a flat top that fits flush with the mated surface. The star drive, also called a Torx drive, has a six-pointed indentation that provides a large contact area for the driver, resisting slippage better than a Phillips or slotted drive. A star drive requires use of a Torx driver for installation and removal.Self-drilling screws, a type of self-tapping screw, are threaded fasteners that drill their own hole and thread it as they are installed. Usually only recommended for use with metal, self-drilling screws are available with wings that enable use when fastening wood to metal. The drill point length should be long enough to penetrate both materials being fastened before the threading portion reaches the material.