Forgefix general purpose pozi screw csk tt zp forgefix csk21410zp these forgefix general purpose pozi screws with countersunk heads are zinc plated for increased durability they are an extremely popular general purpose screw and suitable for use in and with many materials ideal for use in many ironmongery electrical and plumbing applications can be used with various screw cover caps zinc coatings prevent oxidation of the protected metal to create a longer lasting finish it does this by