Thread Bar Bolt without Longitudinal Rib (Prestressed Bolt) : Thread Rebar Bolt is composed of screw thread steel bar , high strength plate ,casting damping nut ,yield tube, washer , and other accessories . According to the structure of steel bar ,the bolt has two stypes : Rib Rebar Bolt and Non-Rib Rebar Bolt . The bolt is usually used in thick coal seam ,that has high stress, large deformation, difficult to support and other poor environment .