Yes the cornerstone is the same size of the outter borders-- 4 1/2". The one border is just laying there.
Originally Posted by Prism99
I don't think it needs a corner setting stone but, of the two pictures you provided, I definitely prefer the top one.
Isn't a cornerstone typically the width of the border?
Edit: Oh, I see that it's a block. I thought at first just the white square was the cornerstone.