Turnstile exit-only doors are also often used in subways and other rapid transit facilities to prevent people from bypassing fare payment. They are similarly used at large sports stadiums, theme parks, and other such venues, to allow pedestrians to exit freely, but not to enter without paying admission fees. These doors usually work mechanically, with the door panels constructed of horizontal bars which pass through a "wall" of interlacing (interdigitated) bars, allowing the door leaves to pass through, but blocking people from illegally entering through the exit.