Where can I get them from? I heard that you can use playing cards also...How would you wedge the cards between the slate and the frame of the table?
i got some perfect mohogany hardwood shims at bowling and billiards. some of those shims at home depot are not "sharp" enough. i used them to shim some center supports for the slate but then to "fine tune" i used the perfect mohogany shims.
http://cgi.ebay.com/HARDWOOD-WEDGES...in_0?hash=item41483a2918&_trksid=p3286.c0.m14
We use these same wedges so i know they are good quality. As for what to do with them once you get them I'd suggest checking out the sticky for leveling 3 piece slate tables.