Hi, So here I am asking my first noob question. I bought a used compressor with a tank but the regulator did not survive the shipping thanks to FedEx. So I have ordered a new one and when I was looking at the pictures of it, I see the inlet and outlet, then there is the gauge on one side. On the opposite side of the gauge, there is another connection point that is sealed with a 1/4" hex head screw. My question is, what is that connection used for? Thanks for any information on that.