The purchased curtain panels are each 40 inches wide. That means we need 3 curtain panels for each window. The new border fabric we purchased is 55 inches wide. I now have two choices, waste 15 inches of fabric on each strip of border fabric or reassemble the purchased curtains to be 55 inches wide. I hate to waste fabric so I went for the reassembly. The first step is to take one of the 3 panels and cut it into 4 pieces. Then I take 2 of the pieces and sew them to each side of a full size panel. This will give me a panel that is 55 inches wide. Repeat the process until you have 8 new panels.
Cut the new panels to length and then sew on the border fabric. Now you have new curtains with lots of seams. Not too lovely from the back, even if you do make nice finished seams.
I have decided to take the easy way out, and Bill wanted the room a little darker, so I will be lining the panels. This will allow me to hide the seams and block out more light, and give a little more insulating protection.