Purchase curtain glide tape for your curtain rods. If the rod is less than 2 inches wide, purchase ½-inch tape; if the rod is more than 2 inches, wide get ¾-inch tape.
Remove the rod from the window and remove the curtains from the rod and set aside.
Apply the curtain tape to the upper side of the curtain rod and smooth it in place with your hands.
Slide the curtains back onto the rod and put the rod back in place.