Backer-On Rock-On Cement Board Screws are designed for attaching HardieBacker or equivalent fiber cement backerboard to wood or light gauge steel studs. The patented serrated head design countersinks for flush seating at any angle, providing a smooth surface for tile. Backer-On Rock-On cement board screws comply with ANSI standards for cement board installation as specified by cement board manufacturers. Backer-On Rock-On screws can be installed with a standard impact or drill/driver and T-25 Star drive bit (included with product) for cement board fastening done right.