I have a friend who needs a room totally dark to sleep. She has drapes over her window, which she keeps closed, and behind that a flat black sheet has been folded over a suspension rod in the window frame. Does that make sense? So, the blinds hide it from the street and the drapes from the room view and she has three layers blocking her from the sun! This would be an inexpensive, no-sew fix (if, like her, you don't care to open those curtains!)