Stairs, stairways, staircases, or stairwells, are building components that provide users with a means of vertical movement with the distribution of separate and individual vertical steps. In a building setting, a flight of stairs refers to a complete series of steps that connects between two distinct floors. Either as conscious design decisions or as reactions to existing spatial conditions, stairs can take on a variety of organizational types from straight runs to spiral, L-shaped, U-shaped, or circular forms. Each stair step is typically comprised of a horizontal tread and a vertical riser.