And then you have one of your partners that insisted that he wanted a drop of an inch per foot on his six foot sluice so I got my four foot level and gave it four inches but oh know...that won't work...we need a six foot level. Go figure. Retired carpenter here so I will give you a leveling tip that comes in handy when plumbing rough framing, etc. Tape a short (couple of inches) piece of 1X2 at the far ends. That way only the two small pieces and not the center touch your studs which sometimes can be really bowed. This gives you an accurate plum wall from top plate to bottom plate. Could be useful on long sluices also. I use this method constantly on my 80in. level. I don't have a set fall on my five inch..I go by how the riffles fill and what I'm suckin' and how fast I'm pumping. And also notice that there can be a big difference when empty vs. full of water and gravel on pontoons.