Timber bolts are often known as dome head or mushroom head bolts and are generally used in wood applications. They are similar to carriage bolts and function the same way. Timber bolts have a larger, round, dome shaped head than carriage bolts and instead of the square neck, they have four fins that sink into wood as the nut is tightened. This prevents the bolt from turning. The oversize head eliminates the need for a washer.
RC Fasteners & Components in your place for Timber bolts in ASTM A307 Grade A, with a hot dipped galvanized finish.