It can be hard to keep a blanket in place. It can pull down curtain rods and using tape can take the paint off the walls (which your parents would hate), and light can still be seen around the edges.
Instead, try carefully taping thick/heavy style aluminum foil to the metal frame around the window glass with masking tape. You'll probably have to use two or three lengths of foil to cover a large window. I think it's easiest to tear them off to the right length, and tape them together on the floor before you try to tape them to the window frame. Have someone help hold the foil for you when you do tape it to the window frame since it will be a fairly large sheet once taped together.
I had to do this once to get sleep in a hotel with very bright windows. Light couldn't sneak around the edges either, and the tape pulled right off with no damage when I was done.
Last edited by Brick7 (July 27, 2010 (11:29pm))