This International Standard, which forms part of the series of standards in the IEC 60300-3series, is the application guide for maintainability. It can be used to implement amaintainability programme covering the initiation, development and in-service phases of aproduct, which form part of the tasks described in IEC 60300-2.It provides guidance on how the maintenance aspects of the tasks should be considered inorder to achieve optimum maintainability. It should be noted that the full programme describedin this standard would only be applied to a major complex product with the potential for long-term usage.For less complex maintainable products, a simpler programme should be adopted by tailoring the programme to suit the degree of complexity and the requirements of the customer. The standard uses other IEC standards and guides, notably IEC 60706, as reference documents or tools to provide more detail as to how a task should be undertaken.Contracts between customer and supplier will vary widely according to conditions and circumstances in different industries. This standard is written on the premise that a product is to be developed by a contractor from a basic concept for the particular requirements of a user when the product is considered to be a development item (DI). However, in many instances, where a product already exists and needs little or no development effort; it is a Non-development item (NDI) and the full maintainability programme as described in this standard will not be required. However, the principles laid down in the standard can be applied as required, by tailoring the maintainability programme to suit the needs of the project.