Well Nuts at Lowes.com
Hillman 5/16-in x 18 Zinc-Plated Steel Hex Nut. Hex nuts are used to prevent shear movement and tension when adhering facing materials together with machine bolts. Hex nuts are commonly used in wood to wood, wood to metal, and metal to metal applications. Grade 2 zinc steel hex nuts are recommended for most general uses and are corrosion resistant.