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

Notice that the line of the wall of the pool is parallel with the sidewalk.

Can you see on the left that the line of the edge of the sidewalk is parallel with the wall of the pool? Well, the Glovers are theoretically standing on that wall. And since it's a narrow perch, we can treat them as a line.

That's just an approximation, but it shows that they are not standing on the wall of the pool. They are standing on the grass. The wall isn't even in sight. They are nowhere near it.  They are well in front of it.