Slender robots, like trunk robots, snake robots, are popular for tasks such as surgery, detection and rescue missions. They have multiple degrees of freedom and flexible bodies, allowing them to operate in narrow and complex spaces. However, the drive system and transmission mechanism remains a challenge in the design of slender body. Compared to other actuation mechanisms, the tendon-sheath actuation system is flexible to adapt to the complex environment. Additionally, it allows for a separate design for the robot’s actuation and drive mechanisms, such that enabling remote operations. In this chapter, we introduce various prototypes of slender robots actuated by the tendon-sheath system. We delve into the design of this mechanism and explore how to control such flexible and slender robot systems. This chapter aims to offer examples and insights for those working on slender robot development, addressing some common design and application challenges.