[Benrubid]

Where my two propane tanks are hooked up, each have a line that hooks up into a central point. At that point there is the switch that you can change from left tank to right tank. My question is below that switch is a plastic cover, that i cannot see what is behind it. I was wondering if that was a spot to hook in a third line for a grill outside? I doubt it because it already has the low pressure line under the stairs. Then i thought that might be where the regulator is. I tried to pull the cover off, but I am afraid to break it. Anyone know what that is under the cover?

Thanks for your help.