Hex Head 8mm hex head countersunk with a fixed washer. Helix & Thread Helix to remove debris and a 50° deep single thread to provide secure fixing with high pull-out resistance. Type 17 Slash The Type 17 Slash to reduce torque and the likelihood of the timber splitting when the screw is inserted close to the edge. Designed as an alternative to the traditional coach screw mainly used for timber to timber applications. Coated with a patented multi-layer corrosion resistant plating, this screw is ideal for outdoor applications. Stainless steel must be used where.