The term 'concrete rod' is a reference to rebar, which is a steel bar or mesh of steel wires used as a tension device in reinforced concrete and masonry structures to strengthen and hold the concrete in tension. Rebar is also known as reinforcing bar, reinforcing steel, and reinforcement rod. It is typically made from carbon steel and is available in various sizes and shapes. Rebar is used in a wide variety of applications, including bridges, buildings, roads, and other structures.