{HEAD ~ A vent hole} in {TAIL ~ the wrap} of the orbiting scroll member cyclically moves over the two grooves 
in
{ HEAD ~ A vent hole } in { TAIL ~ the wrap } of the orbiting scroll member cyclically moves over the two grooves
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH