My recollection, as a teenager in the early 60s, was that in our neck of the woods, the “it” to be sat upon was the other person’s thumb.
We used to say “Sit on it and rotate” along with flipping the bird.
From my Junior High School Coach:
You take the little square of toilet paper. You fold it in half. Fold it again, diagonally. Do that again and you have this little triangle of paper. Tear the top of it off, open the paper and it has a hole in it. Put your middle finger through the hole, stick it up your ass and twirl it around. Pull your finger out and use the paper to wipe your finger as you pull it off.
And people think we don’t know about conservation of resources.