What mechanism is employed by the Aerobridges to dock with the aircraft. I am not looking at how the plane docks but how the aerobridge manages to attach itself over the door of the aircraft? Is it some vaccum tech or what? From outside, one can only see the bellows/ flexible diaphragms.

What I am looking for is actually - how two non-conformal surfaces can be "joined" in order to create a sealed "lock" (assuming its closed from all other ends). This came to my mind and now I am trying to understand this as the situation is almost the same.