{HEAD ~ The pair} of stacks is connected by a length of {TAIL ~ material} which is folded on top of the stacks 
{ HEAD ~ The pair } of stacks is connected by a length of { TAIL ~ material } which is folded on top of the stacks
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH