{HEAD ~ A jacket} is separated from {TAIL ~ the stack} and pushed forward onto an insert unit on a slightly lower level 
is separated from
{ HEAD ~ A jacket } is separated from { TAIL ~ the stack } and pushed forward onto an insert unit on a slightly lower level
HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH