The Eureka! footprints are designed to fit exactly under your tent. Thay not only protect the floor of the tent from rocks, sharp twigs or pine needles, but also from mud and ground water. It can also be used as tarp keeping you out of the rain, wind and sunshine. You can create a functional shelter by using just the fly, the tent poles, and the footprint. This resulting structure will keep off the rain, provides a fabric floor, and has great ventilation at a fraction of the weight of the complete tent.