Multi-thickness blanks (MTB) enable the weight and the design of a part to be optimized thanks to an appropriate distribution of thicknesses and/or mechanical properties. This is usually obtained by adding a reinforcement piece onto the main part, both having been previously cut and stamped separately. With MTB, pre-cut blanks are assembled before being stamped together. This allows, in particular, the stamping and assembling operations to be decreased, with a cost reduction thrown in. MTB's gather tailored blanks, already well known and broadly used, and patchwork blanks which are nowadays mainly at a development stage and give rise to an increasing interest due to their potentialities.