When the curtains you have your heart set on only aren’t wide enough for your window, there is a solution: Stitch two panels together to create an extra-wide curtain. This job takes a bit of attention and time, but it can be achieved with basic machine-sewing skills. It’s easiest to use unlined panels which are simply hemmed on all four sides, but it is possible to adjust the procedure to rod pockets and other header fashions.
Put two curtain panels together, right-sides facing, and upper and bottom hems matching. Pin along one long side. Using scissors or a rotary cutter and mat, cut off the hem on that side, cutting through both panels and the top and bottom hems. Remove the pins.
Open approximately 12 inches of the top and bottom hems of the panels with a seam ripper and beginning at the cut edge of their hems. Iron the opened hems to eliminate the folds and flatten the stuff.
Pin the two panels together, right-sides facing, together with all the cut edges and top and bottom edges matching. Stitch a plain flux along the cut edge, from the very top to bottom of this panel. Use a 1/2-inch tolerance for closely insulation, or even a 5/8-inch if the material is gauzy or loosely woven. Trim the seam allowance with pinking shears to prevent raveling. Press the seam open.
Fold the opened top and bottom hems along the flux to coincide with their initial positioning. Press and pin in place. Stitch the hems throughout the opening, extending 1 inch above the stitching on each side. Pull the thread ends into the incorrect side of the hem; tie in a knot and trim. The enlarged curtain panel is now ready to hang.