The Rocket stove design is a very versatile design that can be improvised with a variety of different materials. The heart of the stove is an elbow-shaped, insulated combustion chamber. The fuel, in the form of sticks or narrow pieces of wood (or even tightly rolled-up paper, if that’s all you have), is fed into the fire on the shelf, as shown. The air enters into the fire underneath the shelf. Because the combustion chamber is insulated, the fire can get very hot, and burn very efficiently.