Remove the cords from the headrail but leave them threaded on the blind.
Lay the blind flat on the table; the right side toward the table.
Measure the width of the blind. Measure the length from the top of the bottom hem to the bottom of the headrail.
Cut a piece of blackout lining equal to the width of the blind plus 1 1/2 inches and equal to the length of the blind plus 2 inches.
Turn the sides of the lining over 1 inch and stitch in place. Turn the top and bottom hems over 1 inch and stitch in place.
Lay the lining on the blind, wrong sides together. The side edges of the lining will be inset from the sides of the blind by 1/4-inch on each side. Align the bottom edge of the lining to the top of the bottom hem on the blinds. Tuck the top of the lining under the headrail of the blind.
Feel through the blackout lining to the rings on the shade, place a mark on the lining at each ring position.
Hand sew through the lining to the ring. Take two or three stitches at each ring location. Take care not to catch the lift cord while sewing. Make a small slit in the lining, just above the top-most ring, and just large enough for the cord to pass through. Pull the lift cord through this opening.
Glue the side edges of the lining to the bamboo shades with clear-drying fabric glue. Use it sparingly; place a dime-sized dab of glue every 4 or 5 inches. Do not press on the lining; that action will cause the glue to seep through to the front surface of the blinds.
Glue the lining to the blind along the top of the lining. The bottom hem does not need to be glued in position.
Leave the blinds flat while the glue dries. When the glue has dried, restring the blind on the headrail and hang it on the hardware.