a lid closing the outlet of the outer chamber when {HEAD ~ the inner chamber} is in {TAIL ~ the first position} 
is in
a lid closing the outlet of the outer chamber when { HEAD ~ the inner chamber } is in { TAIL ~ the first position }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL