The joke he shows Maureen

Have you ever played that little game when you were a kid where you say, "Here's is the church, here is the steeple, open the doors and see all the people." or maybe a more modern version is when one person puts his or her palms together, the other person does the same, and they interlock their hands together perpendicularly between the middle and ring fingers (when one person separates their palms, it looks like an a**hole or vagina. It's the same thing, his finger is rolled in the towel so that when she looks through it, it looks like a penis.