I had some trouble unscrewing the sewer cap on my camper and found some similar plastic wrenches for sale online, which were primarily compatible with the Camco RhinoFlex sewer hose fittings and didn't seem like they would fit my cap quite right. I modeled this to very closely match the dimensions of the lugs on the cap, which don't provide much to grab onto without a tool like this. It worked very well to loosen and then tighten the cap.

Printed on my Bambu Lab P1S in about an hour. Only tweaks to the defaults were 5 top and bottom layers, and a 3 layer side wall. Used ~50g of basic PLA filament.