These are used on headrails that have the white removable stems and gear racks and have an 8 prong aluminum rod running down the center of the headrail.
Vertical blind channel panel clip holds a 3 1/2″ slat for a valance. Snaps onto a headrail that measures 1 9/16″ across the top. This clip will only work with headrails that have a very small lip at 1/16″ or 1.5 mm.