A turnstile is a form of gate which allows one person to pass at a time. A turnstile can be configured to enforce one-way human traffic. In addition, a turnstile can restrict passage only to people who insert a coin, ticket, pass, or other method of payment or verification. Modern turnstiles can incorporate biometrics, including retina scanning, fingerprints, and other individual human characteristics which can be scanned. Thus a turnstile can be used in the case of paid access , for example to access public transport, a pay toilet, or to restrict access to authorized people, for example in the lobby of an office building.