These forgefix pozidriv machine screws are designed for use with nuts or pre tapped holes they are zinc plated for increased corrosion resistance the countersunk head is suitable for pre countersunk holes or when fastening to timber to leave a flush surface applicationideal for use in many diy ironmongery 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 an