The hinges are preferably linear and may be aligned either parallel or slanted in {TAIL ~ relation} to {HEAD ~ the tube axis} 
The hinges are preferably linear and may be aligned either parallel or slanted in { TAIL ~ relation } to { HEAD ~ the tube axis }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD