A covering in the form of a mat or web, comprising a substrate formed as a mesh product or fabric and plastic foam enveloping the substrate which define lines of beaded caterpillar ties, extending longitudinally in a first direction, and rows of thinner connecting ties, extending longitudinally in a second direction substantially transverse to the first direction, with gaps therebetween. The caterpillar ties each comprise a constriction extending continuously along each transverse edge of the respective caterpillar tie between adjacent connecting ties over an upper or lower side of the respective caterpillar tie.