Creating a 3D Model with Tinkercad - 3D Printing: Build your Own 3D Printer and Print your own 3D Objects - page 138

Figure 7.14 Group the three objects so they act as one object.
For a decorative element, I'd like to have a slight “lip” that runs around the outer
edge of the medallion. To do this, I'll make a copy of the larger medallion, paste it
in the workspace, change its height to 1mm, and then place it on top of the larger
medallion. You can see this in Figure 7.15 . (After reducing the thickness to 1mm,
use the black arrow floating above the object to raise it so it's floating at 3mm.)