These Forgefix Pozidriv Self-Tapping Screws have countersunk heads and are Zinc Plated for increased resistance to corrosion. They tap their own thread in to a pre-drilled pilot hole in sheet or solid material. They are single threaded to resist pull-out. APPLICATION:Ideal for use in many DIY, ironmongery, engineering, electrical and plumbing applications. 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 Pozidriv screw is similar in appearance to the classic Phillips cross-head, but in fact is very different. The Pozidriv ha