The easiest way to make a metal (or angle) rod is to cut them out of a coat hanger. Get a parent to help you use a wire cutter to cut the hanger as shown below. Straighten out the handle until you have a right angle. You've got your dowsing rods!
SAFETY FIRST
Tape up the ends of your rods. You don't want them sharp. And don't use them near other people -- you don't want to poke anybody in the eye by accident!
Diagrams of rods by permission of Tom Graves