{HEAD ~ The abutment structure} is attached to the seaming board proximate one of the ends, and is adjustable between {TAIL ~ a closed condition} overlying the upper surface and an open condition away from the upper surface 
{ HEAD ~ The abutment structure } is attached to the seaming board proximate one of the ends , and is adjustable between { TAIL ~ a closed condition } overlying the upper surface and an open condition away from the upper surface
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH