Nails

The traditional New Zealand roof fastener was until 1980 the "Lead Head", a flat-headed smooth shank steel nail with a lead head cast on it. Lead heads often 'backed out' causing leaks, the shanks were prone to corrosion, and lead is incompatible with modern metallic coatings.

Spiral Shank nail fasteners have a galvanised shank, and the spiral shank has over twice the withdrawal resistance of a smooth shanked nail. They are however still prone to backing out, and the under-head seal is not as robust as the neoprene seals used on modern roofing screws.