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