When purchasing used hand tools, the primary focus should be on material integrity and mechanical functionality. For steel tools (wrenches, pliers, hammers), verify the grade of steel, such as Chrome Vanadium (Cr-V) or S2 tool steel, as these retain hardness over time. Inspect for pitting, deep rust, or structural cracks that could compromise safety. For insulated tools, ensure the dielectric coating is intact to meet IEC 60900 standards for electrical safety. Always request high-resolution photos of the working surfaces (jaws, teeth, or cutting edges) to check for excessive wear or rounding.