Rebar (short for reinforcing bar), collectively known as reinforcing steel and reinforcement steel, is a steel bar used as a tension device in reinforced concrete and reinforced masonry structures to strengthen and hold the concrete in compression. Concrete is strong under compression, but has weak tensile strength. Rebar significantly increases the tensile strength of the structure. Rebar’s surface is often patterned to form a better bond with the concrete. The most common type of rebar is carbon steel, typically consisting of hot-rolled round bars with deformation patterns.