At my Ts office door closed me don't interrupt. I have seen the receptionist knock and go in when the door was shut, but she knew that there was no one in session. So, nothing on the door. There is a room next to my t's office that has a sign on it that says do not disturb testing going on, but is the only office I have ever seen a sign on. Also, there is a waiting room all the patients are supposed to sit there until their T comes and gets them. I would def. be thrown off is somebody walked right into my session.