Flipped Fillet Tutorial Question

Question regarding this tutorial
Flipped Fillet Tutorial

At the 1:07 mark circles are added in the corners. The result is circles are placed in each corner at the same relative position. How is this being done ?

Thanks, Bill

The first circle is manually drawn in, then duplicated and dragged into position:


The speed with which the four holes are being added (7 seconds) seemed very fast for manual placement. At least for this old guy :slight_smile:
Thanks for the clarification.