Low point drains -- how to open?
Hello, and thanks in advance for your help for me, here at the bottom end of the learning curve. My wee 14' 2008 (new-to-me) Cruiser Funfinder apparently has low point drains with some kind of way to open them from inside the trailer (on the outside under the trailer, the red and blue pipes have no caps, just open to air). This is what it looks like inside, under the sink. I've twisted and tugged a bit on the rings but without figuring out what I should be doing. I'm reluctant to tug harder for fear of breaking something. HOW do I open the low-point drains?