Technical communicators today must document complex applications used in complex environments. Information about users and use models is important under these conditions, especially if documentation will be presented on-line. Customer partnering, a method of information gathering that supplements surveys, contextual inquiries, usability testing, and interviews, provides one way of involving the users of complex applications in the design of information delivery systems. We used this method to help a client gather important information about user and use models and design a new information library for complex server computer systems.