The Japanese government is establishing an International Rescue Complex to promote research and development of key technologies for the realization of practical search-and-rescue robots, anticipating for future large-scale earthquakes and other catastrophic disasters. This paper proposes a new paradigm called "snakes and strings", for developing practical mobile robot systems that may be useful in such situations. "Snakes" stands for snake-like robots, which can skillfully move among the debris of the collapsed buildings. "Strings", on the other hand, means the use of robotic systems equipped with reels of strings. These strings can continuously supply energy, accomplish reliable communication link, and also exhibit a high traction force. These characteristics are based on the "hyper-tether" concept. This paper shows many new mechanical implementations of snake-like robots developed in our lab, and also explains in detail the new paradigm.