This paper reports on a system that has been developed to facilitate the structure and reuse of engineering rules (ERs) in Knowledge-Based Engineering (KBE) systems. The proposed structure for rule elements supports the traceability of knowledge sources as well as where the knowledge elements are used in KBE applications. This forms the infrastructure to systematically manage the use and reuse of knowledge and control the version and update of the rules when new knowledge is gained. Representing product knowledge in rules is a way to capture the know-why of the design by modelling the decisions involved in the design process. KBE has been used as the mechanism to deploy this knowledge. Although the KBE technology can support the management of this knowledge, the maintenance of the knowledge is often a neglected task. This leads to a number of practical difficulties in the large scale rollout of KBE applications. To design an improved KBE rules maintenance system, the research team developed a generic representation to unify the off-line storage of the IF, COND and CASE statements used in the ICAD Design Language. Additional data fields are defined to maintain the traceability of the origin and use of rules. This is implemented in a Microsoft Access database. The integration of this off-line rule repository with the ICAD KBE system is achieved and validated in an industrial application. The data structure defined and the implementation system is detailed in this paper.