High-Low - For use in plastic, nylon, wood or other low-density materials. Thread design reduces driving torques, enhances resistance to thread stripping, improves pullout strength and lessens the risk of cracking the work piece.
Type AB - Designed for use in the thinner sheet metal commonly used today, particularly in appliances. (Fine Thread)
Type A - For self starting in thin (.015" to .050" thick) metal or resin-filled plywood. Hex Washer Heads are commonly used to hold license plates into plastic. (Coarse Thread)
Type B - For molded or through holes in thin metal, non-ferrous castings. Blunt Point.