A few of us need a little extra instruction.
Go to the mirror and take a long hard look at your butt. Use two mirrors if you need. I certainly did.
Now review in detail this picture.
It's a hole in the ground. Compare and contrast. Your butt and the hole in the ground. Study each carefully.
Continue until you're certain that you know your butt from a hole in the ground. Don't cheat. I needed several passes.