Used mainly for fastening timber to timber and is extensively used for timber joist construction in house building and numerous decking applications. A Carriage Bolt, also known as a Coach Bolt or as a Fully Threaded Cup Square Hex Bolt, has a domed or countersunk head, and the shank is topped by a short square section under the head. The square section grips into the part being fixed (typically wood), preventing the bolt from turning when the nut is tightened. A rib neck Carriage Bolt has several longitudinal ribs instead of the square section, to grip into a metal part being fixed. A round head and a square neck that prevents the bolt from turning while the nut is tightened. Ideally suited for timber to timber joining Hex nut included Zinc plated to increase resistance to corrosion
