The term 'Epitome of Hardness' can be summarized by two crossword solutions: nails and STEEL. Nails are small, thin pieces of metal with a sharp point at one end and a flat head at the other, used for fastening materials together. STEEL is an alloy of iron and carbon, and is one of the strongest and most durable metals available. Both nails and STEEL are incredibly hard and resistant to damage, making them perfect examples of the epitome of hardness.