The authors have devised a method for teaching structural mechanics articulated in three phases: observations (the description of mechanical phenomena, increasingly complex, selected with regards to their pertinence of the problem that one wants to affront, and their efficiency); modeling (the construction of a physical-mathematical model that takes into account its formal content and stresses its importance as an instrument and has the potential for other applications); design (suggestion of cues for applications stimulate the student to exercise his creative imitation). What is proposed to the student is not so much a set of notions, as a method and set of instruments for selecting experiences (for example previous design solutions) to the end of evaluating their repeatability in diverse situations, by means of a physical-mechanical reading which comes from phenomena which one finds in daily life. “Leo” was created as a teaching instrument which is presented as a tale in the form of a hypertext