This International Standard relates to equipment practices. The modular order is applicable to the main structural dimensions of electronic equipment mounted in various installations where dimensional interfaces have to be considered. It refers to basic design parameters and is not intended to be used for manufacturing tolerances or clearances. In addition, information on interfaces to other technical fields, on technology and advanced design aspects is included. This standard also covers standard terms for parts and assemblies of mechanical structures for electronic equipment. This generic standard gives the definitions of a modular order for mechanical structures of electronic equipment and provides for dimensional compatibility at mechanical interfaces with related engineering applications, e.g. printed boards, components, instrumentation, furniture, rooms, buildings, etc. Furthermore, it supports the introduction and application of the modular order rules considering that: – compatibility of interface dimensions is aimed at the electronic field on the basis of the SI unit metre; – technical and economic advantages can be achieved when using the rules. The terms in this standard should be used in all standards for mechanical structures of electronic equipment and in related technical documents.