Service ribbons or ribbon bars are small ribbons mounted on small metal bars equipped with attaching devices, and are generally issued for wear in place of medals. Each country's government has its own rules on what ribbons can be worn in what circumstances, and in which order. This is usually defined in an official document and is called "the order of precedence" and/or "the order of wearing". In some countries, (particularly the U.S.), some awards are "ribbon only", having no associated medal.