Measurements of 10 3/4 " high by 8 3/4 " for the original cut. Sides are 2 1/4 " .

Cuts are made to the intersection points as indicated. A 1/4 " trimming of the 2 1/4 " ends may be necessary

Use a ruler or straight edge to bend the cardboard along the indicated lines.

Use "Elmer's Glue" or equivalent paper glue to glue down the ends outside the nest rectangle. Hold with clothes pins or a weight until dry enough; ~ 30 minutes to hours.