I think 'closed nests' means confining them to a nest with fake eggs, 'open nests' and 'sitters' pen' seems to be what we call a broody coop, again with fake eggs until they do go broody. The burlap (sacking) is to encourage them to stay on the nest during daylight.I will have to come back and read it again later, I didn't understand what encourages them to go broody?