It's like a sluice box except usually you have it on the bank of the river not in the water. It is on legs. Makes it easier to shovel into and has a classifier at the top to seperate out the larger rocks. You pipe water up from the river to run thru it. You can have it high up on the bank - highbanker. By the way, many places don't let you run the water back into the river in any form. You need to either run it into a retention area or be far enough away that it won't run back into the river. You would be in big trouble, fines and possibly have your equipment taken away, if you run back into the river. Know the laws in the area you are working.