Explore a groundbreaking approach to digital fabrication in this 22-minute conference talk from the ACM CHI Conference on Human Factors in Computing Systems. Discover the Cardboard Machine Kit, a set of open-source modules designed to empower novices in building application-specific computer-controlled machines. Learn how this innovative kit, utilizing cardboard frames, stepper motors, and networked electronics, facilitates rapid prototyping of rapid prototyping tools. Examine the results of extensive evaluations, including workshops and real-world usage by over 500 novice builders who created 125 different machines across 15 application types. Gain insights into the efficacy of this modular approach, its limitations, and potential implications for future machine-building infrastructure.