So many variables too deal with .. riffle size,sluice angle,water velocity,sluice width size, i just use my gut feeling for sluice set up you wont find a level,adjustable square,protractor,plumb bob,or ruler in any of my equipment boxes LOL ... your sluice will talk too you if you listen too it... I tryed going with angles and all that other stuff never worked for me .like the Gold Miner spiral wheel they send a piece of cardboard cut too the angle you need too run it LOL no one told the river cons or gold here in Alberta thats how there supposta react LOL and if the water is muddy ... sheesh . Best way too set up a sluice is too use it lots and get too know what your sluicing.. the angle will work itself out ... dont forget too test your tailings, the gold is not lost if it gets washed out its just in a pile 4 feet away LOL