We use a 5 gallon pail, cut 4" off from the bottom go to Walmart buy a tube type float that you inflate. Mount the deflated tube in the middle of the bottomless pail duct tape it so it doesn't slide back and forth. The tube should fit snug without the tape. Position the pail in the pass thru and make sure the tube fits between the TC and truck than inflate. We use a portable compressor and slowly watch to make sure the tube inflates evenly. We have two small dogs that run back and forth from truck to TC trying to be the first thru the pail. They think it's a game. Tube has lasted over 13,000 miles and still holds air. Caution remove before taking the TC off the truck and don't over inflate the tube just snug enough not to let wind and bugs in. Gerry