The best way to sharpen any knives, not just GLOBAL is by whetstone.
But for fine tuning and honing you can use GLOBAL ceramic and diamond steels.
Some do prefer to do full sharpening with these ceramic and diamond steels, but for optimum and most consistent results GLOBAL recommend Minosharp Whetstones.
GLOBAL ceramic and diamond rods are used in the same way that traditional steels are used to sharpen other knives and, as they are made from the two hardest materials known to man, are suitable for sharpening all good quality knives.
The diamond rod is harder than the ceramic rod and will bring back a knife edge quicker.
The diamond rod also will not break if it is hit or dropped unlike the ceramic rod.
However, the ceramic rod will give a finer edge if used regularly.