With no exhaust fan in our bathroom, we usually run the ceiling fan flowing into the camper with the bathroom windows open and door slightly ajar. This is pretty effective in getting fresh air circulated into the bathroom. I wanted some way to provide a permanent solution, but didn't want to lop off the top and bottom of the door nor cut a hole in it. I made spacers for the hinges and latch of .205" birch plywood. I had to provide slightly longer screws for the hinges (not the latch), otherwise this was pretty easy to do. I relieved the plywood slightly for the trim on the door, which can be seen in one of the photos. Based on the thickness of the plywood and the perimeter of the door opening, I calculate approximately 35 square inches of venting. Even with the gap, privacy does not appear to be a concern.