Basically, we preshrink the face fabric and the lining so they aren't going to shrink anymore. Then, we cut the lining the same length, but a few inches narrower than the face fabric. Next we sew the sides of the two pieces together, like a big tube. When we turn the fabric right-side-out, we press the sides so that there is an inch or two of face fabric folded over on each side of the lining. You can then stitch in the ditch, if you like. After the two are sewn together and pressed, we then treat the two fabrics as one--sewing the casing on top and hemming the bottom with the lining a part of both. (If that makes sense). This really isn't any more work than just hemming the sides of the curtains--except, as I've said, I really loathe and fear cutting long lengths of fabric. I intend to dry clean the living room curtains, so I am not preshrinking that fabric--I think washing it will take away the crispness and texture. However, I will preshrink the lining.