ISO/IEC Guide 21-1:2005 provides methods for: determination of the degree of correspondence between regional or national standards and relevant International Standards; adoption of International Standards as regional or national standards; indication of technical deviations which would facilitate immediate recognition of any deviation; numbering of regional or national standards that are identical adoptions of International Standards; indication of the degree of correspondence between the regional or national standard and the International Standard.

ISO/IEC Guide 21-1:2005 does not contain any rules for the use of an International Standard in production, trade, legislation or similar activities. It also does not deal with: the adoption of regional or national standards as International Standards; adoption of regional or national standards as other regional or national standards; adoption of regional standards as national standards; or adoption in or of technical regulations.