here is a link showing a quilter sandwiching on her wall. I know there is a link to a tutorial on how to do this, but I can't find it. Nonetheless, it isn't complicated. Newspaper on the wall to protect it from the spray basting. Tape backing to wall. Spray baste batting to backing. Spray baste top to batting. A few pins here & there to help support the weight of it. then... Voilla! a sandwiched quilt!
http://www.quiltingboard.com/t-39588-1.htm
I haven't sandwiched a quilt since I saw the tute, but I plan to use this method when I do.