This document presents a guide on paper prototyping, an innovative approach used by the Rockefeller Foundation to foster collaborative problem-solving and support organizations in developing transformative solutions to social and environmental challenges. It outlines the process, the benefits of convening diverse stakeholders, and how this method enhances learning, relationship-building, and capacity for innovation among grantees. The foundation emphasizes the importance of early-stage prototypes and iterative feedback in driving impactful change in complex problem spaces.