I have a pretty primitive pulley system that opens the door from outside the run. Also attached to the system is a separate pull that drops a long, heavy bolt across the door to prevent anything from accessing the door once it's closed. My door is pretty small- maybe 8x12". Just big enough for a chicken (or 2, if they're in a hurry) to fit through. I found that the ability to open the door from outside the run was essential because in the morning when I set the chickens loose from their secure house they practically ran me down to get to the feed dish.