Last summer I was at a constuction site and saw these little buggers. Brilliant. Head on over to Mcmaster-Carr (or your favorite supplier) and check them out. Sold as slotted shims and horseshoe shims, they are available in a pleathora of thicknesses, sizes, and materials. They're color coded, standard thicknesses, and reusable. Perfect for leveling a show deck, layout work, or (heaven forbid) getting fugly platforms to bolt together tightly. Also, you can find them in variety packs. (Images were unscrupulously ganked from Mcmaster.com)