Due to the popularization of personal 3D printing, individuals without a technical background have opportunities to manipulate 3D data. However, creating 3D data needs technical knowledge and it is difficult for beginners. Especially when we make practical tools for personal belongings or furniture with a 3D printer, it is difficult because of being necessary to design such tools to fit in with objects. In this paper, we propose WireMolding, a 3D modeling approach for practical personal 3D printing with which sketches can be created to construct a 3D model from the bi-dimensional shape of a physical wire mold. We developed a prototype system and demonstrated the usefulness of this concept at the example of use cases.