Ok we have a barricade high stone wall the sape of a U or a staple or something similar. Two parts of the wall are parralell to each other and a third wall connects the two.
We have a Rebel Trooper and a Stormtrooper. For simplicity's sake, they're the only troopers left in their units.
Each is in base contact with this wall, on the outsides of the paralell walls. So on the outsides of the straight parts of the U.
RAW neither unit gets a cover bonus if they shoot at each other, since they're both in base contact with the same piece of terrain.
That's a bit silly.