This model stair is of a typical steel mono-beam/mono-stringer stair with wood treads. The model is scaled down from a 10" run and 7-1/2" rise model stair. This is to give clients better and physical look/feel for what they might be purchasing from you. This style of mono-beam stair has the tread sitting on top of the stringers while the stringer has a 'saw-tooth' top. Other models are available where the stringer rund straight and the tread looks to slightly notch into the mono-beam. There is also a model that replicated what it would look like with thin steel stringers on both sides and no middle stringer.