Previous scholars have advocated the significant value of sketching in design process-es. This paper first explores how design sketching functions as an agent for design, building on insights derived from both theory and practice. Interviews with professional designers in the field reaffirm the functions and importance of sketching. Not only for designers themselves, but also for their clients and consumers. Given the value of sketching and the variety of stakeholders involved, this paper then aims to structure the affordances of design sketching in a practical framework. Considering that af-fordances must be discoverable and perceivable in order to be effective, this paper subsequently proposes ideas for transforming the framework into a tool that will help designers to discover design sketching and unlock its benefits.