When tightening a steel line fittings what wrench do i use?

When tightening steel line fittings, it's best to use a flare nut wrench or a line wrench. These wrenches are designed to grip the fitting securely around its sides, preventing rounding off the edges. Ensure you use the correct size for the fitting to avoid damage. Always apply torque gradually and avoid overtightening to prevent leaks or damage.