Carriage Bolts are used in wood or metal to wood applications with a domed top and a square under the head. This pulls into the wood as the nut is tightened. When using carriage bolts always use a flat washer between the wood and hex nut to eliminate pull-through of the nut in the wood. Drill pilot hole slightly larger than body diameter of bolt. Insert the carriage bolt so the headed end is on finished side of project for appearance or safety. Length is measured from under head to end of bolt. Steel is zinc plated for moderate protection against rust. Use hot dipped galvanized finish or stainless steel where corrorsion and rust is of concern or for exterior projects.