{HEAD ~ A shutter} that can open and close {TAIL ~ the air discharge port} is mounted on a case 
close
{ HEAD ~ A shutter } that can open and close { TAIL ~ the air discharge port } is mounted on a case
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH