Carriage bolts are fully threaded and also known as shaker screen bolts. They have a low profile head with a square neck that resists turning when nut is tightened or removed. Used for wood-towood and wood-to-metal applications. A square neck keeps them from turning when tightening a nut. A smooth, round head provides a finished look. 18.8 stainless steel has excellent corrosion resistant qualities and are an excellent choice for general use and outdoor applications.