Now there is a Stainless Steel screw that is ideal for attaching plywood or solid wood decking to the metal frames used in truck trailers. In addition to the self-drill tip, wings protrude from the shank and cut a clearance hole in the wood. When the wings hit the metal decking, they fold right up. Nibs on the underside of the head allow the screw to self-countersink. These have a #3 self drilling point which when used with light gauge steel is designed for a total material thickness of .110" to .210". Use 2" Screws for 5/4 (1" nominal) decking and 2-1/2" Screws for 2X (1-1/2" nominal) decking. Threads are 24 per inch. Made of Type 410 (magnetic) Stainless Steel. Taiwan.