The Simpson Strong-Drive SDCF Timber-CF screw is a structural fastener designed specifically for cross-laminated timber construction, mass timber construction and general interior applications. These screws provide uncompromised strength for these demanding applications. The large flat head with underhead nibs provides for clean countersinking. The zinc, fully-threaded screw, with a proprietary “half-point” provides fast starts and excellent holding power. These screws are designed for dry interior use only.