Sharp Little Pinpricks is received in Act 1 you defeated enough Sharps Highwaymen in Lowtown at night. It starts a quest with the same name.

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Directions to the Sharps' Base

We've got a new base and you lot best keep the law away. Directions to the Lowtown sneak below, but don't come unless you've got good news or you'll get an answer square between the eyes.

Ignacio Strand