Just a Single Blind
You know when your room has a window and too much sunlight gets in during the day? This architect decided to keep the sunlight to a minimum, so he invented a single-blind window that gets just the right amount of sun in the room.
The one-of-a-kind widow required a unique blind to cover it. The hardware store would have been quite astonished at the customer requesting just a single-blind. Maybe they sell it separately, or perhaps the designer had to customize a set of blinds for the perfect fit.