I use dowsing mot just for water.

I made my own dower.. one steel coat hanger remove the top hook, cur the remaining steel in half and then the short end straighten to make a L shape. use two own pens remove the ink etc then place the short ends into the pen, allow enough at the bass to bend it to stop the pen from falling down. hold my using the pen not tight and allow the steel to move at will.
A cross is when the 2 cross over each other showing a yes and a strong sign, it the ends turn out wards it is a no and nothing there.

THis works and is also good for any here that use dowsing for other reasons, it does not have to be copper.