The black belts (or midnight blue belts) are called dans and each degree has its own specific name. The dan rank ranges from 1st through 9th degree. In the Moo Duk Kwan, dan level is known by its Korean numeration, such as cho dan (1st), ee dan (2nd) and sam dan (3rd), and onward. In many organizations, the titles of kyosu (instructor 교사/敎師) and sa bom (master 사범/師範) are separately awarded after successfully demonstrating ability, knowledge, understanding and character for that level in a dan simsa (심사/審査), or test. One may not test for kyosu (certified instructor) until 2nd dan, or sabom (master instructor) until 4th dan or above. Dan levels from 4th dan onward are known as kodanja (고단자/高段者), whether sabom or not. Also in the U.S., a simple timing structure was created for the dan ranking system. If in constant study, then it was easy to measure when testing for the next rank. The next dan number was equal to the minimum number of years that must be spent training to achieve that dan. For example, a first dan would have two years before they could be a candidate for second dan, and so on.