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It always happens when you’re in a hurry: vending machines reject your banknote because the corners are folded and dog-eared. Security printer De La Rue has a simple answer (GB 2382325). Banknotes already have watermark patterns, made by weaving the paper’s fibres more densely. Watermarks are normally near the centre of the note, but putting them at the corners increases stiffness there by over 50 per cent. And surface-embossing the watermark increases strength by 250 per cent – so the corners no longer fold and flop.