Well...from what I saw and how the ermm "procedure" was described....the sphincter. Think of a torus and intersect it with another torus 90 degrees to it's central plane but positioned at it's top. The piercing did not project into the anal verge but rather protruded along side it. Now I know what you're thinking: "How the everlovin' fuck do you keep that clean?!" Well, I can assure you they also wrestled with that problem. It was....well.... as you can imagine the stuff of nightmares.