It is used as a sleeve through the camper floor. Cabling and/or pipe is run through this sleeve from the inside of the camper to the undercarriage. The flange at the top is screwed to the floor and just holds the sleeve in place. After the cabling or pipe is routed through, the sleeve is filled with a sealant like silicone. My camper is a 1998 Trail-Lite Bantam. I had to tear out the floor so I am repulling/rerouting most my electrical, gas and water lines that go to the undercarriage. Thanks.