Right hand verge and left hand verge tiles are only to be used with Duoplain tiles. They are an interlocking tile type, and not a plain tile. At right-hand verges and right-hand side abutments, Right Hand Verge Three-Quarter Tiles must be used in alternate courses with DuoPlain Tiles. At left-hand verges and left-hand side abutments, Left Hand Verge Three-Quarter Tiles and Tile-and-a-Halves must be used in alternate courses with DuoPlain Tiles. Specifications Length: 418mm. Maximum Headlap: 125mm. Minimum Headlap: Depends on profile, surface finish and rafter pitch. Material: Concrete. Plug Material: Nylon. Properties Tile finish: smooth finish. Tile profile: interlocking concrete plain tile. Certification BBA certified. DuoPlain Tiles conform to BS EN 490: 2004 Concrete roofing tiles and fittings for roof covering and wall cladding - Product Specifications.