Measure the height and width of the window on the French door.
Cut two pieces of fabric that each measure twice the width of the window by the height plus 4 inches. If your window is 25 inches by 72 inches, cut two 50-inch-by-76-inch pieces of fabric.
Fold the sides of each fabric piece over 1/4 inch and press flat. Fold over another 1/2 inch and press, then pin along the edges. Sew each side along the inside edge.
Fold the bottom and top edges of each piece of fabric down 1/2 inch and press. Fold down another 1 1/2 inches to make a pocket for the rod. Pin and sew along the inside edge.
Attach the sash rods to the door at the top and bottom of each door panel according to the directions on the package. Some rods are tension rods, while others need to be screwed into the door.
Slide the top and bottom pockets of each shade panel onto the rods and mount over the window.
Cut two 6-inch-wide strips of the heavier fabric to make sashes to gather the shades in the middle. The strips should be one-half the width of the window long.
Fold each strip in half lengthwise, right sides facing in, and sew along the long side. Turn right side out.
Tuck the raw edges of the short sides under and stitch along the edge.
Cut a 2-inch strip of hook and loop closure for each strip. Pin and sew the rough half of the closure to the inside of one of the strips, along the edge. Pin the soft, fuzzy half of the closure to the outside of the other edge of the strip. Sew the hook and loop closure in place and repeat with the second strip.
Wrap one strip of fabric around the middle of one of the curtain shades on the French door. You'll gather the fabric in the center to create an hourglass shape with the fabric. Repeat with the second curtain shade on the opposite door.