I just got this FR adjustable tank in the mail last night. I get the basic idea of it, and I think I see how it forms light traps so I can use it in daylight and I'll figure out where to put the sides for the various formats. But, I don't understand why the one corner is square and why the diagonally opposite corner has that little protrusion on the outside. I thought it would be a spout for emptying but I didn't see a hole all the way through (maybe I missed it?) Anybody have instructions for this thing? How much liquid do I need for the various sizes? Best method for agitation to get even development (since I obviously can't invert it)? Thanks, Dan PS Sorry for the lousy photos but they're the sellers, and besides, you probably already know all about this contraption.