When the lid is in {TAIL ~ the first position} it covers {HEAD ~ substantially all} of the top opening of the container 
When the lid is in { TAIL ~ the first position } it covers { HEAD ~ substantially all } of the top opening of the container
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH