Hi, I am in the process of building my coop, mostly of recycled stuff and extra lumber a neighbor is getting rid of. I was trying to come up with an easily opened and closed door from the coop and leading out to the run, without having to access the run each time. I have an old aluminum large dog size dog door, maybe 12" X 17", that has the plastic flap removed (wore out) but it still has the slider to close it. The slider is pretty light weight and I was thinking of attaching a string or chain to lift it open and closed from outside. It even has a locking latch. Has anyone ever used this type door for a coop door? If so, are there any problems using it or hazards? Do you know of any pics? Thanks for the advice.