Extensive re-use of existing code components has long been recognised as a vital step if software engineering is to become a true engineering discipline. Object-oriented techniques offer the promise of simplifying code re-use. We consider it vital that the tools used to support the construction of software match the design methodology. In this paper we present a design for a class library management system which is able to support the object models employed by object-oriented design methodologies. Relationships between classes are modelled using a number of hierarchies (or graphs) and users of the library may graphically browse these hierarchies. Users may also add their own hierarchies. The descriptions of classes are supported through the use of categories and keywords stored with each class for the specified categories. Any number of keywords may be stored with each class for each category. The design enables the simultaneous use of the library with different methodologies.The library may be queried using keywords and will return a number of classes which match the query. A user can then browse, using any of these classes as a starting point. The combination of browsing and querying provides a high degree of flexibility. Basing the descriptions of classes and the relationships between them on existing methdologies will provide a high level of conceptual concurrence between the design process and the use of supporting tools; in this instance, a class library.The paper includes a description of the a prototype implementation of the design, called Melmoth.