There is a full opening with an absence of a top wall providing a top wall edge 113 which makes the top edges of {TAIL ~ the fore and aft end walls} and {HEAD ~ the two angled sidewalls} 
There is a full opening with an absence of a top wall providing a top wall edge 113 which makes the top edges of { TAIL ~ the fore and aft end walls } and { HEAD ~ the two angled sidewalls }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD