During a pre-service of primary school teachers in mathematics in Switzerland, a research team developed an artefact using marbles, boards and, forms in order to let prospective teachers make better links between numeration and the classical algorithm of the multidigit multiplication. Teacher’s knowledge underlying in this algorithm is the distributive and associative laws, the place value and, the definition of the multiplication (Clivaz & Deruaz, 2013; Ma, 1999). These authors highlighted errors due to “move over” the number on the second line of the algorithm. Moreover, the main source of errors is due to the presence of carries (Brousseau, 2010).