A flat-shaped functional overlay for at least one region of a flat-shaped flexible object which does not form a fold when the sandwich composed of the flexible object and overlay is bent towards the side on which the overlay is located is described. The overlay is composed of one or several flat-shaped overlays which are attached to the flexible object in such a way that a part of their surface can move freely relative to the surface of the object covered by this part in the direction of curvature produced when the object is bent.In addition diagnostic test strips are described which have such an overlay.