DIN571 hex head wood screw, also known as coach screw / lag screw. Made of carbon steel. It features smooth shank and coarse sharp wood thread. External hex head allows high torque tightening with socket wrench for heavy timber connection. Widely used for wooden construction, timber beam, fence, decking and carpentry. Pre-drilling recommended for hardwood. Sizes M4~M20, length 20–400mm. Zinc plated / hot dipped galvanized finish available.