dowsing with L rods

Found a swivel, ball-bearing "L" rod...

that is used by the gas companies! My best friend gave it to me several years ago and I had forgotten about it until I was cleaning the house and found it in a box. It's kinda cool-I was testing it outside and a car passed by and the rod followed it! I'm fond of the "Y" rod, but maybe I can have fun with this one.