More than one pin proves fascinating (6)

I believe the answer is:

rivets

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'more than one pin' is the definition.
(I know this)

I don't understand how the remainder of the clue works.

(Other definitions for rivets that I've seen before include "Metal pins or bolts for holding together two plates of metal" , "Steel pins holding metal sheets together" , "Short metal pins" , "Small pins for joining metal sheets" .)

I've seen this clue in The Telegraph.

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