A bulk, generally elastomeric and pliable, layered mat formed to permit selective trimming into size-chosen mat trims / tiles, each of which is structured to perform as a self-puncture(wound)-sealing, defined-liquid-reactive, anti-puncture-leakage coating element applicable bondedly to the outside surface of a selected wall in a container holding the defined-liquid. Also disclosed is a method for protecting against liquid leakage from a puncture wound in such a wall including: (a) preparing a generally elastomeric, pliable, layered coating mat of a self-puncture-healing, defined-liquid-reactive, anti-puncture-leakage material; (b) in relation to a selected container wall, selectively removing, by trimming, from the prepared mat one or more mat trims / tiles shaped for specific use on the outside surface of that wall; and (c) applying and surface-bonding the one or more trims / tiles to the outside surface of the selected wall.