Head: Wafer Head Finish: Zinc Plated Size: 4.8 x 100mm Pack: Box 100 These ForgeFix Phillips Baypole Screws with wafer head are specifically designed for joining PVCu sections, particularly in bay windows. The nails have a self-drill tip and are zinc plated for increased corrosion resistance and durability. The wafer head distributes the load under the screw head, offering a firm positive fixing in a similar way to that of a washer. APPLICATION: The large wafer head distributes the load on numerous types of PVCu sections requiring joining. Zinc coatings prevent oxidation of the protected metal to create a longer lasting finish. It does this by forming a barrier and by acting as a sacrificial anode if this barrier is damaged. Zinc oxide is a fine white dust that (in contrast to iron oxide) does not trigger a breakdown of the substrates surface integrity as it is formed. The zinc oxide, if left intact, can act as a barrier to further oxidation, in a way similar to the protection afforded to aluminium and stainless steels by their oxide layers. The Phillips screw has four simple tapered slots. It is designed so that a Phillips tip screwdriver can turn a Phillips screw with increasing torque. When the torque gets too strong for the tip, the screwdriver tip winds itself out of the screw thus preventing over-tightening and or damage to the screw head. A self-drilling screw is similar to a sheet metal screw, but it has a drill-shaped point to cut through the substrate to eliminate the need for drilling a pilot hole. Designed for use in soft steel or other metals.