Step 1: Drawing the Rim Shape
2. First, draw a vertical line from the center of the curve, down to the edge of the paper. Then, measure the width of the thinnest point of the rim using a ruler and draw the midpoint on the line.
3. Then draw a curve connecting the midpoint to one of the two points where the original curve meets the edge of the paper.
Step 2: Making the Shape
5. Fold the half-circle in half, along the vertical line, and cut along the second curved line you drew to make sure that both sides are equal. You should end up with a shape that looks kind of like a smile.
6. Next, trace the shape onto an old composition book cover and cut it out.
7. Cover the shape with duct-tape to make the shape stronger.
Step 3: The Rim Fabric
9. Trace two brim shapes onto the sweater, and cut them out about a half-an-inch outside the outline. Make sure you don't cut along the inside curve, just cut a straight line across the two points.
10. Place the two shapes right-sides-together and pin along the curve.
11. Sew along the pin line and turn right-side-out.