When we built the run a few years ago, we decided to close the top in with hardware cloth because we have SO many predators here (mountain lions and everything). Well, I didn't realize how happy free-ranging would make my flock. Now, my flock is out all day roaming around, but I still have that hardware-cloth covered run. I hate it except when I have pullets. In the winter, the snow sits on top of it and I have to try to get up there and scrape it off so the whole thing doesn't come crashing down, plus I have to shovel out the run. And, in the spring, the ground becomes a stinky mess just like someone else mentioned in this thread. If I could do it over again, I would cover the run with those clear corrugated panels or else not cover it at all (maybe some bird netting with pullets). Just my two cents!