The top portion 21 of the T shaped valve member 20 forms {HEAD ~ a sealing surface} 30 for selectively substantially preventing {TAIL ~ fluid flow} through the opening 26 
for selectively substantially preventing
The top portion 21 of the T shaped valve member 20 forms { HEAD ~ a sealing surface } 30 for selectively substantially preventing { TAIL ~ fluid flow } through the opening 26
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH