NATO maintains a "standard rank scale" in an attempt to match every member country's military rank to corresponding ranks used by the other members. The rank categories were established, in 1978, in the document STANAG 2116, formally titled NATO Codes for Grades of Military Personnel. There are two scales, though not all member countries use all the points on the NATO scales and some have more than one rank at some points (e.g. many forces have two ranks at OF-1, usually lieutenants):