Creating a 3D Model with Tinkercad - 3D Printing: Build your Own 3D Printer and Print your own 3D Objects - page 130

Figure 7.3 Start with a rectangle for the basic shape of the medallion.
I'd like to add some rounded ends to the medallion to improve the look. To do this,
I'm going to drag in a Round Roof object, as shown in Figure 7.4 .
Figure 7.4 The Round Roof object will give the medallion curved edges.