The pieces I'm using measure 5/8" and they are very sturdy. Check out the link below for an awesome design. I went with this design only on a much smaller scale. The best part is that you don't have to worry about screwing shelves together straight or getting the perfect distance between shelves. They are infinitely adjustable and can be changed anytime. Big thanks to the guys on the Kingsnake forum for this design.
JOSH
http://forums.kingsnake.com/view.php?id=1771208,1771208

