In the early stage of creation, the architect tests his working hypotheses by making many adjustments while designing. During the sketching phase, the existing modelling tools are not compatible with the iterative nature of this process. So the challenge lies in the definition of a model which will allow the whole creative process with its various coming and frowing during the phase of conception. We will illustrate this model by implementing a parametric operator allowing the action of folding. Its parametric specificity will enable the architect, in the design phase, to make the numerous moves alterations required to obtain an optimal shape.