Often referred to as the "coach bolt", the carriage bolt is a round head square neck bolt used to fasten plastic, metal and wood. These bolts have a square neck that differentiates them from other threaded fasteners. Designed to provide a self-locking fixture, these bolts have shallow dome heads to prevent any pull-through. The square neck makes this bolt ideal for security applications such as locks and hinges where the bolt can only be removed from one side. The square neck also prevents the carriage bolt from spinning while the nut is fastened.