I'm attempting to do Peter Sharpe's tutorial, "Streaming Light Rays Room Construction" (http://www.petersharpe.com/Construction.htm) but I can't seem to get my walls to stay on the plane grid when I move them to the far edges of the room. They hover... and if I use the "land" arrow in the object palette, they land more into the plane's center.

Can anyone tell me where I'm going wrong? I'm following the tutorial to the letter... but my walls refuse to stay attached to the floor...

Any assistance with this would be greatly appreciated.

Thanks ever so much! :)