Not sure what your pictures are trying to show. Are you trying to remove/reduce the gap between the top of the rudder and the hull? For that you will have to look at the rudder bearings. They are usually at the point where the rudder shaft goes through the hull (on the inside of the hull) and at the point where the rudder shaft goes through the deck. Depending upon how they are fitted, you may have to loosen some sort of collar before you can push the rudder up. It may be possible to push the rudder up and then slip spacing washers underneath the head of the rudder shaft where it comes up through the deck.