An arch 40 is formed in {HEAD ~ the fold} of {TAIL ~ panels} 36 and 38 so as to create a downward biasing force on flaps 36 and 38, which holds flaps 36 and 38 in contact with base 32  
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An arch 40 is formed in { HEAD ~ the fold } of { TAIL ~ panels } 36 and 38 so as to create a downward biasing force on flaps 36 and 38 , which holds flaps 36 and 38 in contact with base 32
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL 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 OTH OTH OTH OTH OTH OTH OTH OTH