Creating a 3D Model with Tinkercad - 3D Printing: Build your Own 3D Printer and Print your own 3D Objects - page 141

Figure 7.17 The hole is inside the larger medallion.
Next, I select both objects (medallion and hole) and click the Group button. This
blends the two objects—remember that the hole removes material from a solid ob-
ject. What is left over is what you see in Figure 7.18 . It's the larger medallion with
a lip around a slightly lower inner surface.