I have not heard it explained that way .Where did you see it ? Can you give us a link ? In the 90s , meditation teachers stopped teaching "closing down the chakras " because it became evident that closing down all the chakras is not possible except in death . So we tune in or switch on , tune out and switch off as needed . There are protective portals above a circle which are like the double doors of an aviary opening the outer one only after the inner one closes behind the projectors . But in time this happens automatically . I have never had to manually close a tunnel when I project . But I remain curious , so please post a link .