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