This Instructional Activity is a part of the Lesson 11, Unit 9, Grade 7. In this activity, they learn that a trundle wheel is a tool used in real-world situations to measure such distances. From an image and a description of what a trundle wheel looks like, students think about how the tool works and how they could build one. Students think about the tasks for which a trundle wheel is an appropriate measuring tool. This builds on work students did in an earlier unit, when they learned about the relationship between the circumference of a wheel and the distance it travels.