Roofing screw. Designed especially for securing metal roofing to either timber purlins, or to metal purlins up to 2mm thick. This screw has a knurled shank and top thread to ensure good contact between the roofing and the DEKS neo washer. The thread is 13-gauge diameter and 11 threads per inch ensuring high pull-out strength in both timber and metal. The head is 5/16 (8mm) across flats to fit a standard nut-setter.