cost little,save reinforce steel bar,reinforced power,prolong the span The galvanized ... temperrature.Its shapes can be V,U,trapezium or the similar shapes.It has the strong friction ... the stage of use,it can substitute the reinforcing steel bar for pulling. During the stage of construction, ... as mold too.Since it costs little,saves reinforcing steel bar,has reinforced power,prolongs the span so that ...