Inside mount blackout blind.
This is the typical roll down blackout shade, inside mounted. It has a 1/2″ gap on one side and a 3/4″ gap on the other. The bottom rail is fabricated in such a way that there is a 1/8″ gap there as well. We put a valance with side panels, blackout lined. The next step is to attach some trim to the bottom rail of the blind to overcome the light leak there.