Corridors, or hallways, are long passages in a building with doors on one (single-loaded) or both sides (double-loaded). Most commonly used in residential and hotel projects, corridors provide the most efficient horizontal means of access and egress to a large amount of rooms. For high density apartment buildings, hallways are shared between many residential units and connect back to vertical modes of circulation in the form of stair cores and elevator lifts. Corridor widths vary to service diverse demands from single users in private homes to large groups of people in public facilities such as schools and hospitals.