Hex nuts are to be used with machine bolts to adhere facing materials to prevent tension and shear movement. They are specifically useful in wood to wood, wood to metal, or metal to metal applications. Hex nuts made with grade 2 zinc are recommended for most general uses. Parts are finished with a black ruspert coating that provides superior corrosion resistance. This black finish is designed to match the latest trends in hardware. When installing, be sure to pre-drill any holes and to use washers and bolts that are a similar grade and finish. Deck Plus exterior bolts, nuts and washers are ideal for deck building and exterior wood projects.These coated products will not bleed or stain cedar or redwood like zinc and galvanized plated fasteners. Limited lifetime warranty against rust and corrosion.