We're almost finished our chicken coop, but I need a good idea for a pop door. Our pop door is inside the chicken run, which is only 4 feet high, so its very awkward to get in. The door doesn't need to be predator proof because the run is very secure, but we need to be able to open it from the outside. The design also needs to be rugged enough to be able to work in ice and snow, and not let wind in. We have considered a guillotine style door, but are afraid that the snow would freeze it up. A plain swing up door would let the chickens out but not in, and they could freeze in the winter. We considered a plain swing door (hinged at the top) with a locking bar that could slide down across the door, but we were worried about that freezing up as well. Any ideas?