If you were going to design a car, what tools would you use? Carmakers have tried using flashy new computer programs. But to make a really sleek ride, they still depend on something as old as . . . well . . . dirt.

At every major car company—from Mercedes to Tesla to Toyota—you will find sculptors crouching down beside car-like models. They fashion every detail in clay. They use hand tools to form windows, door handles, and the creases in the cars’ hoods. If you peek inside the cars, you will see detailed clay dashboards. They look totally real!

Here’s how car design happens. A designer begins by making sketches of the car he or she imagines. Then sculptors make small models of the drawings. Once a favorite design is chosen, a sculptor makes a model the same size as the actual car will be.

But the models aren’t solid clay. At Buick, sculptors make a car skeleton from foam, plywood, and aluminum. Then they cover it with several inches of warm clay. The clay cools. Finally! It’s time to do the last steps of sculpting design work. Car companies use machines to carve out the rough shape of the vehicle. That takes about two days. Then the sculptors put in all the details by hand—all the way down to the jeweled patterns in the headlights. If a corner is too sharp, it might hit a passenger’s elbow. A clay sculptor can soften it in minutes. Fixing that kind of problem on a computer would take hours!

Gianna Ball is a Buick sculptor. She works on the outsides of clay car designs. She says clay is the perfect tool to work with. You can mold it easily. You can try new things. If your experiments work, great. If they don’t, you can smooth out the clay and start again.