I've only had to do it on a rare occasion when I've determined that it's the same hen that is flying out of the run (it's open at the top of an 8-ft wall). She'll fly to the cross-beam of the man-access door, then figure it out how to fly from there to the top of the wall, and then over. I'll come outside to do something, check on them to feed them, etc., and that one hen will be out, every day, at the same time, greeting me in the open yard. I don't have a fenced property, so I MUST keep them confined inside their run, in order to not have them be a nuisance to the neighbors. So, once I determine which hen it is, consistently, she gets her one wing clipped, to prevent her from flying over the top of the run. It usually works for a while, breaking her of the habit.