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How to install vertical blinds 
Screw holes into the valance. 
The valance is l-shaped so the top surface can be mounted inside the upper frame and the front of the valance will hide the headrail. 
Place the valance on a flat surface with the front of the valance in an upright position.
Measure 3 inches (7.6 cm) from each end and position each bracket so the top edge is against the upright valance. Use a pencil to mark the 2 screw holes in each bracket.