Carriage bolts (also descriptively called round head square neck bolts) generally feature a broad, shallow round head and threading along part of the carriage bolt shank, and is inserted into pre-drilled holes. The square under the head keeps the carriage bolt from turning as the nut is tightened.

Carriage bolts are commonly used in wood and are used to fasten wood parts, or wood and metal parts, together. Carriage bolts are also successful with sheet metal applications, where a standard sized neck may create an obstruction.