ABSTRACT
Three basic parts make up any set of stairs. The treads are what we step on when going up or down. Risers are the parts of the unit that rise from one tread to another, and the carriages are the side pieces used to carry the weight of the entire unit. Steps vary greatly depending upon the type of materials used, steepness, whether they are left open or boxed in, and differences of style. But they generally have those three elements. Long or tall stairs are most commonly made using the stringer technique. In recent years stair units constructed from steel tubing have become very popular. Square tube is a popular choice for metal construction because it is much easier to fit together than other shapes. In general, a hollow tube has much of the strength of a solid structure the same dimensions but much less weight because the interior has been removed.
