My darkroom is in my garage and I had a similar problem. I picked up some light blocking curtains on ebay. It was a year ago so I don't have the name of the seller but the seller was either the distributer or manufacturer and they sold on ebay from time to time. A google search might turn up the source. One of the nice thinks is that they are white (although they are completely opaque) so when I hang them they reflect light back into the DR area. Since they are curtains they have a space at the top for rods that work with those little clips at the end. So when I do darkroom work it only takes a few seconds to put them up. The clips stay on the walls. They come in all different sizes so I found some that go from the ceiling to about 1/2 inch above the ground. The cost was about $25 for a set that was about 8 feet tall and spanned about 8 feet. So I needed two sets to go completely across the garage. I have a smaller set in the back. But for me the beauty is that they come up or down in seconds.