Here's another crude method that works.Dig out the Arc you are trying to establish,into the ground,then lay the rebar over the trench,& while someone is holding each end(with Leather gloves)Step on the rebar towards the middle,& kind of jump on it,until you acheive your wanted shape,also while standing on it in the center,have the other 2,at each end,push towards you,to acheive the arc,& should you pass your objective,it can always be pulled out,by laying the arc on the ground flat,& pulling from each end,kinda' like a Giant wishbone,until you reach your desired Arc.This method works,& is cheaper than a case of Ranier Ale! Good Luck