GAs Water Heater

1. What is the English word for "Jian Ya Fa"?
2. I tried to turn the "Jian Ya Fa" left or right a little bit, but it would not move.  Of course, I did not apply big pressure.  Is that supposed to be really tight?
3. In the event I have to turn off the water coming in and release the hot water from the water heater, should I do something with the "Jian Ya Fa"?  This is just in case if there is a leak.  I was told to turn off the water coming in and turn on the hot water so they come out of the faucets in the house. 

Thanks in advance for your input.