The abutment structure consists of a first element pivoted to one of the opposing sides of {TAIL ~ the seaming board} and an opposing second element pivoted to the other of {HEAD ~ the opposing sides} of the seaming board 
The abutment structure consists of a first element pivoted to one of the opposing sides of { TAIL ~ the seaming board } and an opposing second element pivoted to the other of { HEAD ~ the opposing sides } of the seaming board
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH