Summarize the following:
Any kind of cardboard will work, as long as it's thick and a pin can push through it. Position the pin so it's in the spot where you want the center of the circle to be. Make sure it's secure in the cardboard so it doesn't shift when you're drawing the circle. The larger the rubber band, the bigger your circle will be. If you want to draw a small circle, use a small rubber band or wrap the rubber band around the pin twice. If you don't have a rubber band, you can tie a piece of string into a circle and use that instead. At this point, the rubber band should be wrapped around both the pin and the pencil. Make sure you keep the rubber band pulled taut while you draw the circle so it's even.
Place paper on top of a piece of cardboard. Push a pin through the paper and the cardboard. Put a rubber band around the pin. Place the tip of a pencil in the other end of the rubber band. Pull the rubber band taut and draw a circle with the pencil.