Ferrous steel re-enforcement bars also commonly called re-bar, is used to reinforce concrete and masonry structures, strengthening and holding concrete. It is most often formed with a patterned surface (usually described as deformed) to create a better bond with the concrete poured around it. There are no official deforming patterns, but the spacing, number and height of the marks is standardized and incorporated into the basic rebar standards. There are also plain bars, but these are used in only the most specific ways Rebar is known as a tensioning device because it holds concrete in a compressed state. Concrete is a very strong material when it is in compression, but it has almost no strength where carrying tensile loads is concerned. To overcome this, rebar is cast in poured concrete to carry these loads. Additionally, the design of the rods typically includes the deformity (in the form of heavy ridge patterns) that further support the binding of the rebar to the concrete