There are many types and sizes of prayer wheels. The most common one is a simple hand-held metal or wooden object, from four to six inches long, with a cylindrical body and a metal or wooden axle that serves as a handle at one end, while the other end is wrapped with a roll of paper on which a mantra or prayer is written. The prayer or mantras are repeated in a row, with the length of paper sometimes reaching twenty yards or more. An ornate cover protects the spool of prayers; the prayers cycle and turn with each rotation of the wrist, due to a weighted cord or chain. It is customary to turn prayer wheels in homes first thing in the morning and last thing before bed in the evening, and many people carry and rotate one while walking throughout the day.Most common in Tibet, they are sometimes even referred to as "Tibetan Prayer Wheels" or "Mani," derived from the mantra or prayer "Om Mani Padme Hum." Tibetan Buddhists believe these words sacred and its recital, silently or out loud, evokes a powerful, spiritual and benevolent blessing. Traditionally, even though the wheel itself and its practical uses for carts were known from other cultures, the Tibetans considered the wheel very sacred and did not allow its use for any other purpose other than that of the prayer wheel.
