Cardboard prototyping uses cardboard, foam board, tape, and other cheap craft materials to build physical models of products, spaces, or service touchpoints. It applies the paper prototyping philosophy to the third dimension: get something in the user's hands as quickly and cheaply as possible, even if it looks nothing like the finished product. The material constraints of cardboard force designers to focus on structure and interaction rather than aesthetics, which is exactly where the most important design questions lie at the early stages of physical product development.