Four shaping biface experiments, using various hammers, allow us to revisit the theme of the criteria for identifying percussion techniques in the Acheulean. The four experiments were done with old antlers, fresh antlers, hard stone and soft stone (sandstone). The flakes from the shaping, around 40 for each experiment, are characterised in a database in which metric, weight, flake, profile and edges morphology (4 criteria), ventral and dorsal data (5 criteria), numerous buttom data (7 criteria) and bulbar zone data (5 criteria) are listed. The flint used is regional (Senonian chalk) in order to feed and apply our results as closely as possible to those of the various sites of the Hauts-de-France region which delivered a full bifacial chaine operatoire.