Here is the metal version of this jig for sharpening straight gouges on the wet grinder.
It's made out of two big washers, bolted on a steel core. The core is 12mm wide, same as the bar diameter.
I mainly use it for smaller gouges than the previous.
Edit : I just realize I did a mistake on the above picture. It should be used with the bar between the two washers. (you know, sometimes, even in great movies, there are mistakes)