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Ordinary fictional storeroom plan. Two labelled rock-display silhouettes, S and T, lie beside a printed centimetre scale. S spans 0–4 cm and T spans 0–6 cm on the supplied diagram. The plan asks, “Which labelled silhouette has the longer base in this drawing?” The same scale, left-edge zero convention and base direction are used. A sealed display cannot be scratched or opened. The supplied readings are retrospective: they are not children's prior predictions or measurements of actual rocks. A separate optional classroom job uses two large plain paper rectangles, chosen by the adult, to practise a real ruler procedure.