The forgefix phillips fine thread wafer head drywall screws are zinc plated for increased durability they come complete with a phillips no2 insert bit the screws have a self drilling hardened point designed for fitting dry linings to steel framework without drilling pilot holes 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 th