A Gau (also spelled Ghau or Gao) is a Tibetan Buddhist amulet container or prayer box, usually made of metal and worn as jewelry. These small containers are used to hold and carry sacred amuletic objects such as images or mantras (prayers), or as a reliquary. They can be simple or elaborate, with precious or semi-precious stones and are often decorated with Auspicious symbols or mantras.
Clamshell style Gaus are hinged on the top and open from the bottom.
Fitted back Gau styles have a friction-fit back which can be pried open with your fingernails.
Traditional style Gaos are ostensibly friction fit, but usually tied with string to keep the two sides together.