I have a generator that lives in my mud room that I use for power outages. When I need it I wheel it out onto the back porch and run this fatty cord through the door and plug it into the aux panel. It's always been a pain because of course the door won't shut with this fat cord running through it. So here is my solution. I designed this thru wall port for the cord to run through. It is a tube (green) with a flange to come through the outside of the house (siding is green) then another tube (white) that slides through the wall from the inside and slides over the green tube. It's a nice snug fit. Then there is a plug to plug the hole when it's not in use and a split bushing to go around the cable and fill the tube when it is in use. My goal with this 3d printing hobby is to make useful stuff, not just trinkets and doo dads. I am pretty happy with the way this turned out.