Modeling is important in object-oriented software development. Although a number of Computer Aided Software Engineering (CASE) tools are available, and even though some are technically advanced, few developers use them. This paper describes our attempt to examine the requirements needed to provide tool support for the development process, and describes and evaluates a tool, Knight, which has been developed based on these requirements. The tool is based on a direct, whiteboard-like interaction achieved using gesture input on a large electronic whiteboard. So far the evaluations have been successful and the tool shows the potential of greatly enhancing current support for object-oriented modeling.