http://blog.makezine.com/archive/2009/11/13/KS%20engineering%20stock%20%23256%20aluminum%20sheet%20template%20for%20pneumatic%20bridge.pdf Make: Projects - Pneumatic trough, part I http://blog.makezine.com/archive/2009/11/make_projects_-_pneumatic_trough_pa.html 2009-11-13 http://makezine.com/images/logos/rss_icon.jpg