Abstract. Current input technologies for wearable computers are difficult to use and learn and can be unreliable. Physical interfaces offer an alternative to traditional input methods. In this paper we propose that developing a well-designed physical interface requires an exploration of the psychological idea of affordance. We present our findings from a design study in which we explore the natural affordance of a cube and suggest possible requirements for the design of graspable cubeshaped physical interfaces as alternative rich-action input device. We expect that such a framework will enhance the precision and usability of devices for wearable and mobile computing.