Measure the portion of the sofa cover you want to accent with cording with a measuring tape. Cut a length of cording that corresponds to that measurement, plus 2 inches for overlap. Set aside.
Fold one of the raw edges of the fabric over to meet the selvage edge, right sides together. The folded portion should be shaped like a triangle. Press with the iron.
Use the yardstick to draw several lines diagonally across the triangle. Determine the width of the line by doubling the width of the cording and adding 1 inch. If your cording is 1/4 inch wide, draw a line 1 1/2 inches from the edge of the triangle and continue to draw lines spaced 1 1/2 inches apart across the fabric.
Cut out the fabric strips along the lines.
Place on strip of fabric on top of the other, right sides together. Line up the short edges so that the strips form an upside down "V." Stitch the edges together and repeat until you have sewn all the strips together into one long strip.
Place the long fabric strip down, wrong side up and place the length of cording down in its center. Fold the fabric over the cording to conceal it.
Stitch along the length of the strip, as close to the cording as possible.
Pin the piping to the couch cover, with the cording on the left side and the excess fabric to the right. If you need to fold the piping around a corner, clip a small "V" into the excess fabric to ease it a long the corner and prevent bunching.
Clip the extra cording, so you have 1 inch remaining when you get all the way around the cover. Overlap the ends of the piping and pin in place.
Stitch the piping to the cover, staying as close to the cording as possible.
Fold the cording over the excess fabric and press in place to conceal the raw edge.