I took a copper pipe and cut one end of it in half longitudinally. I then flattened it out and ground and bent the shape needed for the keeper. It worked but it really only held the slotted nut in place for removal and placement.
Latter it was worth the wait to get a Park Tool CNW-2. But then again, it really only held the slotted nut in place for removal and placement.
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No matter where you're at... There you are... Δf:=f(1/2)-f(-1/2)