Simpson #7 3" Self-Drilling Siding Screw, 410 Stainless 1000PkModel No. F07T300TDM Coating Material. Type 410 Stainless Steel Screw Size. #7 Length (in.) 3 Head Diameter (in.) 0. 230 Drive Type. #1 Square Head Type. Trim Head Thread Length (in.) 2 3 TPI. 19 Point Type. Drill Point Packaging Qty. 1000 The common application for this screw is for attaching wood siding, wood panels and metal trim to steel studs. Features include a trim head, #3 drill point and #1 square drive. Key Features Trim head. #3 drill