The block member moves from a first position to a second position by contact with the slider sliding in {HEAD ~ a sliding direction} to block and open {TAIL ~ the air passage} 
to open
The block member moves from a first position to a second position by contact with the slider sliding in { HEAD ~ a sliding direction } to block and open { TAIL ~ the air passage }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL