Here’s a great article I found by Diane Marcotte from the Canadian Society of Dowsers about Dowsing, and Dowsing Tools:
Dowsing is the process of using a tool such as a pendulum or rod to discover things that cannot be discovered using our everyday senses. It is a term, which in the past has been associated primarily with the finding of water sources. Modern dowsers dowse for oil & gas, minerals, water, lost objects, lost people with perhaps one of the most common uses today being the use of a pendulum to determine one’s state of health and whether particular medicines, supplements, etc. should be taken.
Dowsing Tools
A dowsing tool is nothing more than a communication device. In and of itself it has no power and no ability to move. Although no one knows how or why dowsing works, it seems that the movement of the pendulum or rod(s) is controlled through or by your subconscious (or something of that nature). Most experienced dowsers use all the basis dowsing tools. These are the pendulum, L-rods, Y-rod and the Bobber with the first two being easily made from materials on hand. Any object hung from a piece of string is a pendulum and a old wire coat hanger can be cut and bent into a L-rod. The tool chosen is usually just the most convenient one for the job at hand. As dowsing devices come in all sizes, shapes and materials, it is important only that you choose a tool that you’re comfortable with for all instruments work equally well for experienced dowsers.