1. Aligning midpoints, sew border strips to long edges of table runner center, beginning and ending seams 1/4" from corners (Diagram 2). In the same manner, sew remaining border strips to remaining edges.
2. Referring to Diagram 3, lap one border strip over the other. Using the edge of an acrylic ruler, mark a diagonal line from the border seam corner to the intersection of the strips' raw edges (Diagram 3). Place the bottom border strip on top and repeat the marking process.
3. With right sides together, match marked seam lines and pin (Diagram 4). Beginning with a backstitch at the inside corner, sew together the strips, stitching exactly on the marked lines. Check the right side to see that the corner lies flat. Trim excess fabric, leaving a 1/4" seam allowance. Press seam open (Diagram 5). Mark and sew the remaining side border corners in the same manner.
4. To miter each end corner, lap one side border strip over the other and mark and sew as before. Check the right side to see that the end lies flat. Trim excess fabric, leaving 1/4" seam allowance. Press seam open (Diagram 6). Mark and sew the remaining end corner in the same manner.