Applies to new equipment practices. "New" in this context refers to new developments agreed between manufacturer and user. Applicable to the main structural dimensions of electronic equipment mounted in various installations where dimensional interfaces have to be considered. Refers to basic design parameters and not intended to be used for manufacturing tolerances or clearances. Not intended to introduce any changes in existing equipment practices. Covers object, terms and definitions, fundamentals, modular order details and application of the modular order.