Each individual reinforcing bar is manufactured with a series of individual markings: The top letter or symbol identifies the producing mill and deformation pattern. The next marking is the bar size. The third marking symbol designates the manufacturing material - usually either "S" for carbon-steel (ASTM A615) or "W" for low-alloy steel (ASTM A706).

Finally, there will be a grade marking (4 or 5, for 420 or 520) or by the addition of one line (420) or two lines (520) that must be at least five deformations long.

Bar tags provide the key to identifying rebar. A typical bar tag shows the number of pieces in a shipment of each bar. It also shows that the materials used to manufacture the bar conform to ASTM standards for reinforcing steel.