In this work, certain task designs to enhance middle school students' spatial visualisation ability, in the context of an instrumental approach, have been developed. 3D modelling software, SketchUp®, was used. In the design process, software tools were focused on and, thereafter, the aim was to interpret the instrumental genesis and spatial reasoning processes of two students on the use of the software tools. In the application of the tasks, it was observed that the students were easily familiar with certain tools; however, they were not good at some and needed instrumental reinforcement. Additionally, the student whose spatial ability performance was better than the other could easily accomplish manipulation of the tools. In light of the obtained results, certain recommendations are made.