After the body of the quilt has been pieced, gently press before adding borders. The logical place to measure the finished top is along its outside edges, and this is a useful measurement. However, measurements should be taken across the center in two or three places for both the width and length. If these measurements are different from that of the outer edge, accidental stretching has occurred. To keep the finished quilt as straight and square as possible, you must measure the centers.
To make a border with straight-cut corners:
Determine the length of the quilt border by averaging the distance of two or three center measurements (see Fig. 1). Cut two borders that length and pin them to opposite sides of the quilt matching ends and centers and easing in the fullness. Sew and press.
Determine the width of the quilt border by averaging the distance of two or three center measurements (see Fig. 2). Cut these borders that length and pin - easing in the fullness. Sew and press.
To make mitered comers, consult a quilting book that contains instructions for finishing a quilt.