A new product concept emerges in communication between participants in a design process. We will study this concept design, focusing on how designers communicate using artifacts and space to mediate their understanding. During the design sessions artifacts are used for argumentation and gestures are used to act out how the suggested features work. We make conceptualizations on the dynamic concept design process to delineate the relationship between the arena of ideas and how these ideas are concretized. In order to succeed in a geographically distributed situation a computer support system must be able to mediate this kind of communication in product concept design. The paper develops an idea on how to support designers' spatial communication by computers.