When sourcing used sheet piles, you must prioritize Section Modulus and Moment of Inertia, as these determine the structural load-bearing capacity. Inspect the interlocking mechanism (Larssen or Z-type) to ensure they are not deformed, as damaged clutches will prevent water-tightness and proper installation. Additionally, verify the remaining wall thickness using ultrasonic thickness gauges to account for historical corrosion, and ensure the steel grade (e.g., S355GP, ASTM A572) aligns with your engineering requirements.