Any physical model can potentially be a prototype. The difference lies in how closely it reflects the intended finished part.
Very simple models can be made with paper, plastic, modeling clay, styrofoam, balsa wood, or other common household materials. These are examples of very low-fidelity prototypes, but they do have the advantage of being easy and inexpensive to make.
These types of prototypes would likely not function very well or for long, so they’re used primarily to get a visual idea of the design and to compare it in scale to other parts.
More high-fidelity prototypes use modern machine tools and materials, including various 3D printing technologies, vacuum casting, rapid tooling for injection molding, and CNC machining.
