I HIGHLY recommend using these guys if you're doing fab work with multiple pieces of sheet metal. I'll be watching them myself, but I don't want to bid against anybody here -- and I have a handful already.
I called them Kleekoes because I hadn't ever seen the term written ...
http://cgi.ebay.com/ebaymotors/Cleco-Fastners_W0QQitemZ190106334734QQihZ009QQcategoryZ26442QQrdZ1QQcmdZViewItem
Here's how they're used: