Abstract
This study extends instrumentation theory by examining how spatial artefacts support Year-3 students’ development of multiplicative thinking through composition and decomposition. Drawing on classroom observations, we trace students’ instrumental genesis—how they reconfigure artefacts (instrumentalisation) and develop utilisation schemes (instrumentation). The findings show a trajectory toward deliberate product composition and flexible decomposition, laying the groundwork for distributive reasoning. We introduce spatially mediated instrumental genesis to characterise this spatially grounded scheme development.