Backer-On 23405 1-1/4 in. Zinc-Plated Flat-Head Square Screws (800 Pack) to Attach Cement Board to Wood or Light-Gauge Steel Studs Use to attach cement board to wood or light gauge steel studs Ideal for use with Showers, backsplashes, Countertops and floors Deep square head allows for a confident drive Countersinks for flush seating Corrosion and rust resistant for long lasting durability