The SHBOBGRR2X4 Guardrail Receptacle bolts directly to the Bridge Overhang Bracket or to the Overhang Bracket Extender and allows the easy installation of an OSHA required lumber guard rail post. The 2x4 Guardrail Receptacle ships with two ½”-13 UNC x 3” long electro-galvanized bolts and nuts for attachment.