Oswald in the doorway: the blog of the Oswald Innocence Campaign, by Ralph Cinque

In this case, we are not talking about the shape of a whole object but just one quadrant of it. Think of it as a sphere with a square quadrant. 

That, in effect, is what we are looking at:

I am saying that shape of the junction of his forehead and the top of his head is perpendicular. It is an angle, but it is also a shape. 

And it is very different from the shape of Billy Lovelady's head.