**Materials:**

* square dowel, or any piece of wood with a rectangular or square cross-section, 10-inch length (or more) * two nails with heads, roughly 1 inch long, not too thin * string, preferably non-stretchy * ruler with metric system (cm, mm) and a pen or pencil * hammer * scissors

**How to construct an ellipse maker:**

1. Hammer the two nails into the piece of wood, both on the same side. You get to pick how far apart you want them. Different separations will give you different shaped ellipses. Three or four inches might be good for starters. 2. Cut a piece of string that's at least twice as long as the separation between the two nails. The longer the string, the bigger ellipse you'll get. Ten to twelve inches might be good for your first experiment. 3. Tie one end of the string to one nail and the other end to the other nail. Now you are ready to draw an ellipse!

**How to draw an ellipse with your ellipse maker:**

1. Place the piece of wood, nails up, on a piece of paper. Center it on the paper and hold it down (it may help to have a partner do the holding). The string attached to the nails will be loose. 2. Take a pencil and use it to stretch the string out as far as it will go in any direction, then touch the pencil tip to the paper. Keep the pencil vertical. 3. Keeping the string stretched out as far as it can go, and the pencil tip on the paper, move all around one side of the wood until you've drawn half of your shape. Then lift the string to the other side of the nails and repeat the process to draw the other half of the shape. Depending on how long your stick was, you may need to lift it up to connect the two sides of your ellipse to complete the shape. You did it! You have now drawn an ellipse.

**Things to try:**

1. Try putting the nails farther apart or closer together and drawing another ellipse. How does it compare to the first one you made? 2. Try using a shorter or longer piece of string. What difference does the string length make in the size and shape of the ellipse you get? 3. Experiment with the nail separation and/or string length to see what will make your ellipse look almost exactly like a circle.