Used for securing galvanised steel sheeting. The convex washer covers the hole made in the sheet by the shank of the nail. The twisted shank gives greater resistance to pull out created by the flexibility of roofing materials in windy conditions.
Easily driven, twist threaded nail best suited for wood joints with substantial lateral or racking loads. Recommended for fastening hard woods and end-grain wood without splitting. Used in conjunction with plastic roofing washers to secure corrugated sheeting.