Around the runner 44 is {HEAD ~ a plurality} of {TAIL ~ pivotally disposed stretchers} 45 for supporting the ribs 45 
Around the runner 44 is { HEAD ~ a plurality } of { TAIL ~ pivotally disposed stretchers } 45 for supporting the ribs 45
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH