The steel self-drilling screw with black oxide finish has an 82-degree oval head and a Phillips drive. Steel is often used in applications where strength is the primary consideration. The black oxide finish offers mild corrosion resistance and lubricity. The oval head has an 82-degree cone shape for a flush fit in a countersunk hole and has a slightly rounded top that sits above the mated surface. The Phillips drive has an x-shaped slot that accepts a Phillips driver and is designed to allow the driver to slip out of the head to help prevent over-tightening and damage to the thread or fastener.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.