A dog-leg is a configuration of stairs between two floors of a building, often a domestic building, in which a flight of stairs ascends to a half-landing before turning at a right angle and continuing upwards. The flights do not have to be equal, and frequently are not. Structurally, the flights of a dog-leg stair are usually supported by the half-landing, which spans the adjoining flank walls. From the design point of view, the main advantages of a dog-leg stair are: