wherein the pair of {TAIL ~ fifth rollers sandwiches} the pair of second bent parts and is mounted so as to slidably contact the pair of second bent parts of {HEAD ~ the intermediate rail} 
wherein the pair of { TAIL ~ fifth rollers sandwiches } the pair of second bent parts and is mounted so as to slidably contact the pair of second bent parts of { HEAD ~ the intermediate rail }
OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD