Forticrete Hardrow 457mm x 686mm Duet Tile & Half - Barley Please note that deliveries to Scotland for this product will incur additional delivery charges. Please note this is the tile & half for the 457mm x 457mm hardrow duet tile in barley. Tile & half are laid at the start and finish of every other course. Dimensions Length: 457mm. Width: 686mm. Thickness: 14mm. Fixings For pitches below 40 it is possible to hang the slates, depending on conditions, but advice can be sought from the roofing superstore technical department on 01752 692760. Above 40 all slates should be nailed into the batten with 2 x 38mm x 3.35mm aluminium nails (40mm x 4mm for 24 x 18 slates). The nail hole diameters are approximately 5mm with the nail holes being approximately 50mm down from the heads of the slates and 50 - 100mm in from the side edges.