This traversing structure has been designed to span across the width of the adjacent doorway and to appear as thin as possible. The 4.5m long blade is constructed from a series closely spaced cross section ribs held between two layers of laminated plywood. The ribs add structural depth and taper to allow the formation of a thin leading edge. Two supporting legs provide stability and are located to optimise the bending moment within the spanning/ cantilevering blade.