Originally Posted by The Griz
No, #5 is the screw. Look on the right hand side of the image. It has a key, showing #5 as being the screws that hold #3 (the Safety Valve) on.
Ok, #3 not #5. Still wondering what #21 is. There is no break in that hose from the canister back to the valve/tank.
Edit-- see the small in-line valve now over in the key, I must not have looked closely enough at the hose.