The age gate is the screen asking each visitor to confirm being twenty-one or over before any portrait appears; every woman on the roster meets that line too.
A gallery of portraits like this one should not open to anyone who happens to click. The age gate is the first screen on the site: a visitor states that they are twenty-one or over, and only then do the roster, the prices and the rest of the catalogue become visible.
Everyone listed on this wall is twenty-one or over. The same line applies to every guest, and to anyone else who will be in the room during a session, and sending a booking message is the guest's statement that this is true. The figure sits above the age of majority by choice, because a rule written to protect people works better with room to spare than drawn at the edge.
A click on a button proves very little, and the house does not pretend it does. When she arrives, the woman you booked may ask to see photo identification. She glances at it and returns it at once; no copy, scan or photograph is made, and nothing on it is written down. If she cannot satisfy herself that everyone in the room is twenty-one or over, she leaves before the session starts and the visit ends there. A reservation arranged as a present, for a friend's birthday or a stag weekend, holds the person receiving it to the same line as the person paying.
The gate also explains the tone of everything behind it. Because a visitor has already confirmed their age, the profiles, the prices and these definitions can speak plainly, and a guest reading about a pair booking or a night need not wade through euphemism to learn what it costs.
The age verification page explains the gate in more detail, the FAQ covers related questions, and the roster describes the women the gate stands in front of.