{HEAD ~ a cylinder} with {TAIL ~ two independent, opposing shafts} that assumes two characteristic positions: 
with
{ HEAD ~ a cylinder } with { TAIL ~ two independent , opposing shafts } that assumes two characteristic positions :
HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH