Plain Concrete Iron, commonly called concrete bone iron, is one of the building blocks for structural concrete. Generally, there are 2 types of rebar produced, namely round bar and deformed bar. The difference between the two types of iron is the surface. Plain iron is iron that has a round section with a smooth or finned surface. Meanwhile, screw iron has a special surface shape in the form of transverse fins (fish fins) whose production is done by twisting.