I am certainly feeling a little stupid, but I cannot seem to get this propane matter straight. We are coming out of a motorhome, where a gauge told us how much gas was left in the tank. We now have a 5th wheel with twin 30# tanks and automatic switch over. I know of course that when one tank is empty, the system will automatically switch to the full tank. The red/green indicator will be red. Here is my question: Below the indicator is a knob that points either to the left or right tank. Does that knob have any function other than to remind me which tank is the empty one? I remember being told to move the knob to the full bottle when I remove the empty one. (Since the full tank will be already in use, that is what leads me to think turning the knob is only a reminder). So, itâ€™s far from rocket science, but I need the answer. In addition, if the knob does NOT control anything â€“ how would it be possible to select the tank you want to use? Unlikely that would occur, but humor me. Thanks.