In this paper, we present a new method dedicated to hot forging. We show how to supply automatically the three-dimensional preforms sequence from the rough product. Our method uses a methodology coming from French forging industries. In particular, it implements rules and know-how related to this trade. We present the main steps of this method which are relative to form feature extraction, to knowledge representation, and to geometrical concerns .But, in this study, we only focus on our bi-dimensional outlines representation and how hot forging know-how is using on it. An industrial casestudy is developed that validates our concepts and this case-study has been approved by local blacksmiths.