Here is a picture of the "official" wrench. The problem is that it wears too quickly. A number of people here have bent and ground their own, and have a better, longer lasting wrench. I have a diagram somewhere here which some body posted. I'll see whether I can find that too. But for right now, the picture, or maybe a bit later.
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The next job will be finding the directions to make one, but that will come after dinner.