I found these small flints on country walks and I think they have been worked into 'thumbnail scrapers'. The name is from their size; to give you an idea, the red arrow is 1 centimetre. I don't think any one really knows what they were used for, but they are very interesting objects.
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in reply to your flint discovery
I expect these tiny sharp flints were put in the tips of an arrow type weapon. No good trying to re-sharpen something needed to be light and accurately aimed, so just replacing the tip would be like having the end sharpened. See your handy local archaeologist and save all the tips. Take a metal detector with you, next time, you might get something of value if it's an area of ancient activity.