According to one preferred embodiment of this invention, centerline 60 comprises a weld that joins {HEAD ~ the two layers} of {TAIL ~ flexible sheet} 20 
of
According to one preferred embodiment of this invention , centerline 60 comprises a weld that joins { HEAD ~ the two layers } of { TAIL ~ flexible sheet } 20
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH