Found on 1963-67 Corvette hardtops, this shim sits partially under the rear weatherstripping as it interfaces with the upper & lower rear window brackets. The head of a special screw rests on the shim at the top & bottom (center) of the rear window. Sold individually, some 1963 tops require only one at the top of the rear window, while all 1964-67 hardtops have one at the top & bottom.