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I found this strange looking bit in a bit set of uncommon bits, including Security Torx, hexalobular, tri-wing, spanner head, 12-point flange, Torq-set and others. It's the only one that I could not identify, what is it for?

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Good quality photos like that are liable to psychologically damage the average newcomer who thinks that photos should be small scale, unfocused and lit by a distant candle. And your question is also liable to give typical newbies conniptions - while it is short it is to the point, we know what you are asking and the picture and text match. Much more of that and some of the longer serving members may also feel threatened. Keep it up :-) !!! – Russell McMahon Mar 19 at 15:19
up vote 20 down vote accepted

My first thought is that it might be intended to be a wing nut driver of some sort, but those are usually hollow cylinders with slots for the wings.

Ah ... sure enough, it's described as such in this Ebay ad:

enter image description here

share|improve this answer case using hands to fasten/unscrew the wing nut provides too much torque, you can use the screwdriver handle to reduce the torque applied? ;-) – SF. Apr 26 at 9:47

It can also be used for fastening the 'eye' of hook and eye fasteners into wooden frames.

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We're looking for long answers that provide some explanation and context. Don't just give a one-line answer; explain why your answer is right, ideally with citations. Answers that don't include explanations may be removed.

That's what I thought too when I first saw it. Could be because my fingers are currently sore from installing such a hook by hand. – Carlton Mar 20 at 5:52

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