Thread Diameter 0.112" Head Diameter 0.212" Head Height 0.067" Phillips Drive #1 18-8 Stainless Steel provides strength and offers good corrosion resistance in many environments. Flat head has a flat top and a taper. Flat heads are designed to be used in a countersunk hole. Sheet metal screws have sharp threads that cut into a material such as sheet metal, plastic or wood. They also make excellent fasteners for attaching metal hardware to wood because the fully threaded shank provides good retention in wood.