Flap barriers, also known as flap gates or flap turnstiles, are access control devices commonly used to regulate the flow of people in various settings such as office buildings, transit stations, airports, and stadiums. They consist of vertical panels or flaps that rotate on a horizontal axis to allow or restrict passage.

These barriers typically feature two or more flaps arranged in a line within a housing or frame. The flaps are connected to a mechanism that allows them to rotate in one direction only, usually in a single or bidirectional mode. To gain access, individuals must present a valid credential such as a ticket, access card, or biometric authentication, which triggers the flaps to rotate temporarily, allowing passage. After the authorized individual passes through, the flaps automatically return to their closed position to prevent unauthorized entry.