Rebar is commonly known as hot rolled ribbed bar. The grade of ordinary hot rolled steel bar consists of the minimum yield point of HRB and grade. H, R and B are the first letters of hotrolled, Ribbed and Bars respectively. Rebar can be divided into three categories according to strength :HRB300E, HRB400E, HRB500E, HRB600E, etc.

Steel reinforcement bars or rebars are used to improve the tensile strength of the concrete, since concrete is very weak in tension, but is strong in compression. Steel is only used as rebar because elongation of steel due to high temperatures (thermal expansion coefficient) nearly equals to that of concrete.

Rebar (short for reinforcing bar), known when massed as reinforcing steel or reinforcement steel, is a steel bar used as a tension device in reinforced concrete and reinforced masonry structures to strengthen and aid the concrete under tension. Concrete is strong under compression, but has low tensile strength.