International audienceIn this research study, we investigated how middle school students created 3-dimensional objects from 2-dimensional figures using an extrusion method. In a summer enrichment program, students used manipulatives and a dynamic geometry program (Cabri 3D). We identified students' strategies for forming 3-dimensional objects with a focus on their gestural signs. The results demonstrated that they most often employed dynamic-pointwise and dynamic-objectwise gestures to demonstrate the lateral faces or edges of 3-dimensional objects. Also, students linked their gestural signs and the Segment tool of Cabri 3D to indicate their reasoning
