The invention relates to a shim for insertion between the facing surfaces of two parts, in which the separation between the parts is variable with position along the facing surfaces. The shim includes sections that are juxtaposed in a direction transverse to the separation, at least some of the sections are strippable shim sections that include a stack of sheets which are adhered to one another by an adhesive. Slits between individual strippable shim sections allow selective removal of sheets from respective sections, altering shim thickness with position along the facing surfaces.