Flat Truss TypesUsed when positive drainage is required to one side only. This shape is often used for Industrial, Commerical and Farm applications. Sloping Chord FlatFor positive roof drainage. Many variations are possible as shown, the selected shape will depend on the particulars of the project. The depth for estimating span to depth ratio is measured at 1/3 span from the smaller end. Sloping Chord (Valley) FlatUse this shape for roof drainage to centre of roof. Building Designer must size down pipes to prevent ponding on the roof. For this truss the depth is measured at the least depth location.