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