Flare nut wrenches are made differently from regular open end wrenches. They are more like a 6 point box wrench, but with a slot i them to allow them to fit over the line. They also tend to be much thicker that a std wrench. This is to prevent them from rounding off the fittings. This is what they look like http://www.sears.com/shc/s/p_10153_12605_00942012000P?vName=Tools&cName=Hand+Tools%2C+General+Purpose&sName=Wrenches
