Hermit, it is not to lock them in permanently. We've built them a huge run, but have been debating whether to build them arks to sleep/lay eggs in (hubby wants to build arks) or give them huts. I know the headroom can be an issue, so needs to be tall enough etc. He thinks it is easier and less expensive to construct. I have only used huts, so don't know anything about the merits of arks, apart from the mobile ones, that you can move the hens around each day, for fresh pasture. These would be fixed, and we'd shut them up at night, as lots of foxes here. They will have a huge fenced off area for through the day. You sound like you are happy with yours, chrismahon? Are yours just for the mobile groups?