In its simplest form, a Dowsing Pendulum is nothing more than a weighted object at the end of some type of string or chain that weighs less than the weighted object. This creates a situation where the pendulum is capable of swinging freely when someone holds the chain and allows the Dowsing Pendulum free range of motion.
Most pendulums you purchase are made of some sort of metal chain or heavy cording. The "bob" aka "pendulum bob" can be made of virtually anything as long as it is heavy enough to keep the chain or cording taunt while using it. Most people prefer the bob shaped in a consistent way. This is to ensure balanced weight across the entire bob to prevent interference with free movement of the pendulum.
Some of the more commonly used materials for the bob are crystals, metals or other gemstones. Usually pendulums are flat on top and tapered to a point at the bottom. Occasionally you will see other shapes such as round, square, triangular, or freeform shapes. Many believe the odd shaped pendulums do not “swing true”, meaning the unbalance weight from the shape can pull the swing out of alignment. You should decide which feels correct for your use.
To allow the bob to swing freely, it needs to hang. Most people use either a lightweight chain or some type of thread or cording. In an emergency, you can use a long hair and a ring from your finger.
Some people that make pendulums bestow various powers upon them. Practitioners of Witchcraft and Wicca, other magical affiliations and energy worker, tend to be some of the groups that do this.
Before using, cleanse your dowsing Pendulums of negativity or empower it to focus on specific items or types of items such. Examples include a Pendulum keyed to dealing with financial matters, health concerns or any other specific thought or item. This is similar to charging a ring, pendant or other piece of jewelry with a magical power. The main difference is the purpose is more for locating the object versus bringing the object to you.