For fixing timber to steel purlins, the JCP Woodfix Roofing Screw from Fixaball combines a countersunk head with a winged shank and self-drilling point. This zinc plated fixing is suited to light and heavy section steel, with options covering steel thicknesses from 1.2mm-3mm and 4mm-12.5mm. The countersunk head sits flush with the material, while the wings create a clearance hole in the timber to reduce the chance of jacking during fixing. A Pozidrive drive is stated in the product name, and the source also refers to a Torx head. Key features Thread diameter: 5.5mm Finish: Zinc plated Countersunk head Winged shank creates a clearance hole in the timber For timber to steel purlins Self-drilling tip Specifications Light section Point type: 3 Steel thickness: 1.2mm-3mm Heavy section Point type: 5 Steel thickness: 4mm-12.5mm Sizing 5.5mm x 40mm, max fixture thickness 22mm 5.5mm x 50mm, point type 3, steel thickness 1.2mm-3mm, max fixture thickness 32mm 5.5mm x 60mm, point type 3,...