thats TO LOGICAL))))))not to sound like a smarta$$ but I've seen lots of shops simply use Lowe's long arm and flush hinges. *shrug* I'm sure lots of sign suppliers have them but why not see what your local hardware store sells?
Matthew
BlackIceFX
found these on the Internet in about 3 seconds of searching: http://www.graphicsignsupplies.com/misc_hinge.asp
I've used them before, but can't remember who I got them from...
Carol