Corrosion-resistant, stainless steel tongue and groove board screws. Lost head allows the screw to be driven without a pilot hole and into the tongue without splitting the board. Features a twin thread tip, providing a balanced and true start. Tri-Lock TS (twin and single) thread eliminates timber split and the thread form prevents boards from lifting. Seats beneath the tongue, resulting in a neat, flush fix. Can be removed. Also ideal for exterior cladding and boards. Supplied with a TX10 driver bit.