A Y-shaped twig or rod, or two L-shaped ones, called dowsing rods or divining rods are normally used, and the motion of these are said to reveal the location of the target material.
Many water witches back in the day used nothing more than a forked stick (aka a dowsing rod) to search for groundwater because they believed that these were simply channels for their power.
Dowsing is a technique that allows one to detect vibrations or subtle fields present in people, objects, and places. It relies on the natural human ability to perceive energetic frequencies that escape the physical senses but can influence our well-being and our environment.
Dowsing: What It Is How It Works and What Its Used For | Gaia
Founded in 1961, ASD has spent decades exploring and teaching the secrets of dowsing—an age-old practice used to locate hidden water, minerals, and even lost objects with little more than a simple rod or pendulum.
dowsing, in occultism, use of a forked piece of hazel, rowan, or willow wood or of a Y-shaped metal rod or of a pendulum suspended by a nylon or silk thread, in an attempt to detect such hidden substances as water, minerals, treasure, archaeological remains, and even dead bodies.
"Water dowsing" refers in general to the practice of using a forked stick, rod, pendulum, or similar device to locate underground water, minerals, or other hidden or lost substances, and has been a subject of discussion and controversy for hundreds, if not thousands, of years.
Dowsing’s roots go much deeper than that, and much farther back than the tools we now associate with dowsing, such as the pendulum, forked stick, or dowsing rods (L-shaped bent rods).