The do-not-disturb sign in an airport room
The do-not-disturb sign, or its button by the door, keeps housekeeping and turndown from knocking. Set it before she arrives, not once the session begins.
Every airport hotel room has some way to tell housekeeping to stay away: a card that hangs on the outside handle, or a button on a panel that lights a small indicator in the corridor. Either way, the message is the same, and hotel staff respect it.
Why it matters in airport hotels
Many airport hotels run an evening turndown service between about seven and ten. Staff knock, and if nobody answers they let themselves in to fold back the bed and replace the towels. That round runs exactly when most evening sessions take place. Without the sign, a knock at twenty past eight is a real possibility.
When to set it
Before the therapist arrives. Once the session has begun, nobody wants to get up and go to the door. Many guests set it at the same moment they close the curtains and switch off the ceiling light.
Going one step further
For a long session or an overnight, a short call to reception to decline turndown and early morning service is worth making. No reason is needed. The room is simply marked in the housekeeping schedule.
If a knock comes anyway
Say through the door, without opening it, that you do not need anything. Staff hear that dozens of times a day and move on.
In the morning
Leave the sign on until you leave, if you intend to sleep after the session. Then take it off as you go, so the room is cleaned for the next guest. The journal note on the knock at nine covers turndown in more detail.