Get a black heavy duty garbage bag and before unraveling it (swoosh, swoosh!) cut the bottom off. Now unravel it (swoosh, swoosh!). Take a pair of scissors and cut it straight down the side. Now you have a huge tarp that will be great in blocking light! I taped these bad boys up over my windows that before would have been lighting up thr whole block but now... Voila! Even when its completely dark outside there isnt the faintest bit of light creeping through. And during the day, theres just a window with the blinds closed Dont buy the same thing pre cut for umpteen dollars!