the deck surface (see illus. gallery below) is presently of renewable planking: a double file of approximately one-thousand, five hundred eight-foot two-by-fours each, on edge, upon a framework of nine longitudinally laid stringers of one-foot iron i-beams, topped with bolted-on wooden cladding, whose ends rest on the two abutments. attached beneath these are fifteen transverse floor-beams, from which vertical lattice pillars, under tension, translate the live thrusts of traffic to the bowed upper chord, which transfers this back as tension along the bottom-chord "string" of the bow. this bottom chord consists of two sets of four 10 cm x 3 cm wrought-iron eyebars, running along, outside, both sides of the deck. although originally two-lane, due to the weight and frequency of modern traffic, the blackfriars is at present two-way but single-lane. because of damage to the wooden deck surface and to the iron structure, it has been closed to automobile traffic since 2013.