Turnstiles.

Turnstiles, revolving doors and portals are used in applications including stadiums and arenas, perimeter and interior security, recreation and amusement parks, retail crowd control, transit fare collection and entrance access control .From a business/revenue standpoint, turnstiles enable a venue to have an accurate, verifiable count of total attendance. From a security standpoint, they lead patrons to enter single-file, so security personnel have a clear view of each patron. This enables security to efficiently isolate potential trouble or to confiscate any prohibited materials. Thus, turnstiles are a tool which leads to a more safe and secure atmosphere throughout a site.