Marketing InformationZip-in's® sophisticated heat treat process allows the screw to taper to a fine, sharp point without sacrificing critical point strength. A single starting thread (1) is machined down to the very tip of the point and is the source of Zip-in's® penetrating power. A second thread (2) above the point engages after initial penetration and moves the screw in double fast. Zip-in's® screws are faster driving, with a greater capacity for fastening heavier gauges of sheet metal than any other self-drilling type.