Trivial question of the day. I want to add a flap/door to the vent on the back side of the coop on the outside to prepare for the winter. There is one more upper vent that is basically a cold air return on the top of the side wall that you Can barely see on the vright side of the picture. I am a bit concerned to close the back vent off, but also am concerned to leave it open. If I hinge on the bottom, it will be always open or closed. If I hinge on top, i will need a hook to keep it open, but I could add a chain to keep it partially open. What do you think? There is mesh on the inside.