The Twist-Lock Driver is specifically designed to manually install the Twist-Lock Single Screw Stud into fiberglass or wooden surfaces. The comfortable cellulose acetate handle is large enough to grip the tool and apply sufficient turning force. A fluted handle design keeps the tool from rolling off when not in use. Please note that pre-drilling a hole is recommended prior to installation. For wooden surfaces, a #7 screw typically requires a 7/64" drill bit for pre-drilling. For most fiberglass applications, a 1/8" drill bit is advised. As this is a manual driver, it allows the installer to gauge the amount of pressure needed to drive the threaded screw into fiberglass. If the installation force appears excessive, the installer should stop and slightly enlarge the pre-drilled hole to prevent spidering or gelcoat crazing in the fiberglass. Sailrite also recommends chamfering the pre-drilled hole in fiberglass to further reduce the risk of spidering. To ensure proper sealing (bedding) of the fastener in fiberglass and prevent water leaks, use “Trimmable Butyl Tape.”