[JRTJH]

The J wrap on the bottom of the trailer sides is open from below. You can use coroplast and build a "box" to secure to a couple of outriggers. Leave the back slightly open so you can reach in and store the sewer fitting and reach in to get it out again. It'll be outside the trailer, nothing else in contact with it and yet easy to get to. I built one on my trailer and installed a 6x6 compartment door in the J wrap to access both the dump valves and the sewer fitting. It's been in place 5+ years and still going strong. Coroplast is a lot more durable than most people think, and it's also as easy to work with as cardboard.