Every regular blackout blind fails in the same place — the small gap between the fabric and the window frame, where daylight slips through and lights up the room. Our cassette system closes that gap on all four sides. The aluminium cassette seals the top of the window, side channels grip the fabric edges tight against the frame, and the weighted bottom bar meets the sill. Once the blind is down, no light gets past — which is the difference between “almost dark” and the kind of dark you actually need for real sleep, a proper film night, or a nursery that stays dark past 6am in June.