When setting up video calls, Daily offers different levels of privacy, including public rooms where anyone can join, and private rooms that require specific permissions to enter. The company's "knocking" feature allows participants without meeting tokens to request entry into a private call, which is enabled by default for all private rooms but must be explicitly turned on. This feature uses meeting tokens, which are created using the REST API or in the Daily dashboard, and can be used to join calls through a room URL, an app's UI, or programmatically with the client SDK for JavaScript. The knocking feature has different user paths depending on whether participants have valid meeting tokens, and it is available in both Daily Prebuilt and custom UIs built with the client SDK. To build a custom knocking feature, developers will need to use specific methods and events provided by the Client SDK for JavaScript.