I’ve got only flat stones right now. I’ve been asked to sharpen a Zero Tolerance 0301 which has a slight concave section in the blade.
Can I sharpen this with the flat stones, or are curved stones going to be required?
The flat stones can handle way more recurve than that. You will be just fine!
I have sharpened this knife, and its Kershaw brothers, about 10 times. So yes, it can be done with the flat stones 
. The key is to somewhat use the corners of the stones and not to use much pressure.
I am typing this on a phone, so it’s a bit awkward to search for similar threats. But this question has come up before. If you want to try for yourself, do a search on “recurve”. Use the search tab in the top right and not the search box.
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