I THINK if you push the one round plunger down for pressure, you can lift it up by holding the finger down. be careful, it might hurt you if it flips back up. I have one something like this on one of my machines. I don't know what the screw part does. It probably holds the pressure down, after you push the plunger down. Not sure.
Last edited by barny; 12-22-2015 at 07:47 PM.