In the loop

Long ago, we’d go to The Museum of Science and Industry in Chicago.
I loved the Mathematics Exhibit, which demonstrated all kinds of principles of mathematics.
One of the displays had a large Moebius strip, and a red arrow ran along the twisted loop to demonstrate that the geometric construct had only one side.
“Let me demonstrate with my belt,” said a man. He took off his belt and gave it a twist. “See? It’s a Moebius strip.”
It was when he pulled down his pants that my parents realized he wasn’t a volunteer, and they shouted for museum security.