A revolving door typically consists of three or four doors that hang on a center shaft and rotate around a vertical axis within a cylindrical enclosure. Revolving doors are energy efficient as they prevent drafts, thus preventing increases in the heating or cooling required for the building. At the same time, revolving doors allow large numbers of people to pass in and out.
Around the center shaft of the revolving door, there are usually three or four panels called "wings" or "leaves." Large diameter revolving doors can accommodate strollers and wheeled luggage racks.