Hey
These four points are a way of entering the Image, a starting off point where the eye naturally goes to. The "hook" if you like, is to put an element of your composition, that you want the viewer to see, on one of these points.
very nice
On this Image, my "hook" lies at the end of a path,as you walk down there I want you to look at the texture of stone, the columns on the left take you up to the ceiling. The crossing arches lead you down back on to the path.
Becouse you have to travel
through the Image, to get to the "hook" this also gives the Image depth.
Check out the paintings of Jan Vermeer.