A particle board screw is hardened and fully threaded when under one inch in length and threaded approximately ⅔ of the screw length when over one inch in length; it also has a tapered shank. They have asymmetrical threads and are often waxed or have some form of lubricating agent applied. Asymmetrical threads resist slippage and pull out. Particle board screws are available only in steel, but in a variety of platings. They come with and without Type-17 points. Most are flat head but there are some round washer and pan heads as well. They come square, Phillips, and combination drives.