Bridge Fasteners has been a leading supplier of Fasteners, nuts, bolts, stainless hardware and contractor products for over 30 years. Quality you can trust! Truss head screw has a head with a flat underside and a slightly domed top. It has almost no exposed edge.This makes for a great clean look when using this fastener for an exposed application. Sheet metal screws are also the go to fasteners for use with plastic wall anchors in drywall. Tapping screws are considered externally threaded fasteners that "tap" their own mating threads in metallic and non-metallic (such as plastic) materials. Tapping screws, especially Type A, are referred to as "sheet metal screws" because one of their first applications was in ventilation ducts made of sheet metal. They also make excellent fasteners for attaching metal hardware to wood because the fully threaded shank provides good retention in wood.