Reflecting upon the constructionist model "learning-bymaking," prototyping (prototype making) as a product design and research approach is well recognised for assured development of innovative concepts in individual or collaborative working environments. A prototype is typically used as a tool to support experiments or interventions and to evaluate research goals. It also facilitates participatory design and user-centred design. However, it carries both coded and tacit knowledge that we, design educators and practitioners, find problematic to explain and instruct, particularly to non-designers. This paper amalgamates and argues the characteristics of prototyping including types, formats, and principles through literature review. Reflecting upon the designer’s intentions and the dual coding cognitive learning process, the author proposes a descriptive model that illustrates the dual actions experienced by the designer which can enable study on the improvement of the prototyping process.