In this paper we want to investigate Dynamic geometry Environment (DGE) in primary school. DGE is a way to develop powerful mathematics knowledge thanks to its ability to visually make explicit geometrical concepts. This theoretical possibility to better understanding geometry is not so easily to be shared by students in the classroom. The aim of this paper is to expound the epistemic value of DGE when reproducing figures in geometry in primary school, as a didactic milieu. Situations are designed by teachers and researchers in a cooperative engineering, based on habits and geometrical knowledge (didactic contract). Then they are implemented in the classroom. The shared understanding is a way to highlight geometrical properties. Doing so we want to show how the limits during teaching class when reproducing figures may be exceeded thanks to the DGE and a deep understanding by the collective of teachers and researchers.