This study investigates the use of manipulatives by elementary students working on a fraction task. Extending previous work on the role played by the manipulatives in students' activity, we aim at describing how the choices made for the task design disrupt students' activity, creating opportunities to learn. The theoretical underpinnings allow envisioning the students' activity through the concept of routine and the manipulatives through the concept of affordance. The analysis of the students' mathematical activity allows us to better understand how manipulatives can serve as breaching elements, leading students to modify their mathematical activity, and thus, creating opportunities to learn. [For the complete proceedings, see ED630210.]