I'm with PatriceJ. I use anything round in my house that will give me the curve I want for corners....pots, plates, glass (for small projects)...anything that is round. A pot lid is good. My girlfriend wanted circles on a quilt she was hand quilting. She used a big iron skillet. I haven't done scallops, but I bet I could measure out the length and find something in my house that would be the right round item. You can also, use one of those math compass tools for smaller circles and use a pin with a string and a pencil/pen for larger ones.