The back side of the blue blocks looks like it has a thick 2" wide rubber band on it - that is what contacts the door frame. You twist the entire thing to unscrew it and pressure fit it to the door frame.
The metal brackets go around the door stop (moulding on the door frame) and into the blue blocks. All they do is keep the blocks from twisting when swinging hard.
The door still shuts with the pressure bar in place (and is mounted high enough we don't walk into it) so once in place, you only have to take it down when you want to take the bar somewhere. (we remove the swing when we are not there to supervise).