I used the Eleanor Burn ruler for mine. It comes with very helpful instructions. I can't get to mine right now to give you the exact name of the ruler. The helpful advice I was given was not to make the scallops too "deep". In other words a soft curve, especially for your first ones so that it is easier to sew on the binding. I was so excited about how mine turned out! I never thought I would be able to do a scallop border. Good luck with yours!