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!
Here's what I did: 1) Take a white bed sheet and cut it in half. Fold the bed sheet as many times as it takes to get it small enough to fit over the window without a huge amount of overlap onto the surrounding walls. 2) Tape the white bed sheet to the walls surrounding the window using white duct tape. Make sure, of course, that the blinds are drawn. 3) Get some BLACK plastic sheeting and do the same as with the white bed sheet. 4) Get a sheet of "foil faced foam sheeting", i.e., insulated foam board. You can get this at ANY building supply store. Next, you're going to cut strips of the foam board in order to build a box around the window. So, cut strips about 4-6 inches wide by a little longer than the window frame. Now, place the foam board strips ON THEIR SIDE so the 1/2 inch (or whatever thickness you get) is facing the wall surrounding the window frame, and the 4-6 inch width is sticking out from the wall. This will form the "box" frame around the window. Use your white duct tape and tape the 4, 4-6 inch wide, strips around the 4 window sides--again wide side (the 4-6 inch width) facing OUT from the wall. You should now have a "frame" surrounding the window (made of the foam board) which stands out from the wall 4-6 inches. Finally, cut a piece of foam board that will fit over the window. Tape it to the foam board "frame" which sticks out from the wall 4-6 inches. You have now created an insulated foam board frame and box to cover your window. Not only is this COMPLETELY light tight, the insulating qualities of the foam board help keep the room cooler in warm weather, and warmer in cold weather. Also, the foam board will cut down SIGNIFICANTLY (perhaps essentially completely) on any possible heat signiture coming from your windows. I think a lot of people don't realize just how much heat or cold is radiated into a room through the windows. Bud