Automative tools and systems for knowledge acquisition and refinement are primarily designed to relieve the well-attested burdens of knowledge engineers. The knowledge acquisition process may benefit from greater participation by the domain expert. A survey of automative knowledge acquisition tools and systems provides a context for end-user knowledge manipulation systems (EUKMS). Software support for knowledge acquisition achieved by EUKMS is presented. If given a pre-defined domain model, the implementation of elegant graphical user interfaces to knowledge-bases, a technique for the automatic conversion of a user's rules into code, plus browsing and editing facilities to modify the rules, represent a significant advance in the development of systems which enable a non-programming knowledge-worker to create and refine rules, without the mediation of knowledge engineers. A key element of EUKMS is knowledge representation at the interface; knowledge is externally represented to the knowledge-worker using domain familiar abstractions, language, and objects, which map to an internal, machine representation of knowledge, concealed from the user. An application of the approach in the creation of a system for the interpretation of speech spectrograms is discussed. The outcome of this application suggests that EUKMS are achievable and have an interesting role in knowledge acquisition for complex domains.