Hilman Hex Bolt Hex bolts are machine bolts that have been designed to adhere facing materials to prevent shear movement. Specifically in wood to wood, wood to metal, or metal to metal applications. Zinc grade 2 hex bolts are recommended for most general uses and are corrosion resistant for typical use. Be sure to pre-drill any holes and to use washers and nuts that are a similar grade and finish. Hex bolts are machine bolts that have been designed to adhere facing materials to prevent shear movement. Specifically in wood to wood, wood to metal, or metal to metal applications. Zinc grade 2 hex bolts are recommended for most general uses and are corrosion resistant for typical use. Be sure to pre-drill any holes and to use washers and nuts that are a similar grade and finish.