Cut, trace, or stencil all sorts of shapes quickly and easily with the Circles, Ovals and Rectangles Shape Templates by Fiskars. There are three templates in the package. Use them with the Fiskars Shape Cutter (sold separately).
Fiskars Shape Template - Circles Ovals and Rectangles
These templates are really easy and simpe to use. The only problem I had was due to me not having the blade down far enough, but a few turns and it works perfectly. The blade cuts cleanly every time for perfect circles, oval and squares.