There are the 3 basic stack positions for vertical blinds, draperies, and vertical honeycomb shades
Stack positions are oriented looking at them from the inside, where the vertical blind is mounted. The Left stack position has the vane slats drawing to the right, where the vanes can be tilted closed. The Split Stack position, sometimes referred to as center open, draws the vanes to the center. The Right Stack position has the vanes drawing left. Stack position is an option when ordering a Vertical Blind Headrail.