Ok I understand this problem of "topology" (?) thx for the explanations!
< So for instance, to remove a window, don't create a box - instead select the side pieces of the window and delete them. Then select the open edges of the window and delete them too, removing the hole - now the window is erased and the original surface is restored in that area. You can only delete edges if they are not attached to something else, so that's why you delete the side pieces of the window in a first step.

You say "side pieces" it's well the "sides faces" not the "edges" side? (due "only delete edges if they are not attached to something")

I have delete the "faces" side prime and that works :)
But something will be very cool in this case (and useful in many other cases of course) : a "loop (or ring) selection" faces (or edges) :)
Is that possible?