High Quality Content by WIKIPEDIA articles! A rebar (short for reinforcing bar), also known as reinforcing steel, reinforcement steel, rerod, a deformed bar, reo, or reo bar, is a common steel bar, and is commonly used as a tensioning device in reinforced concrete and reinforced masonry structures holding the concrete in compression. It is usually in the form of carbon steel bars or wires, and the surfaces may be deformed for a better bond with the concrete.