Hex bolts, or hex cap screws, are large bolts with a six-sided head (hexagonal!) used to fasten wood to wood, or metal to wood.
Hex bolts, also called hexagon screw head bolts, hex cap bolts, hex-cap screws, or machine bolts, are a very common choice when it comes to construction and repair. Hexagon screw head bolts come in a large variety of sizes and diameters.