The bloke I knew did not use rods, just a little weight on the end of a bit of string. You could ask it yes or no questions and it would revolve clockwise for 'yes' and anti-clockwise for 'no'

On the Randi show he was given an OS map with all the legends removed and divided into an 8 by 8 grid and he had to pick the grid that had an ancient monument in it. He had no problem.