Stairs, also known as a stairway, a staircase, a stairwell, or a flight of stairs, is a structure used to bridge a large vertical distance by splitting it into smaller vertical distances known as steps. Stairs are used in architecture and engineering to provide access to upper levels of buildings, vehicles, or other structures. Steps are used where horizontal travel is required between two points that are not close together. They are usually but not always open to the public. Examples include sidewalks, streets, pathways, terraces, and rooftops. Steps can also be found inside buildings, such as those leading from one floor to another or from one part of a building to another. Steps can be made of stone, wood, plastic, or metal. The choice of material depends on how much use the step will receive and how attractive you want the step to be. There are three basic types of steps: straight-backed, curved, and angled. Straight-backed steps are the most common type and are easiest to build. To make them, first measure how many inches high you want your step to be. Then divide that number by 2 if you want the step to be flat (not raised at all). If you want the step to have a rise of 1/4 inch or less, then multiply the number by 2 again.