Fingers are items used in the Rocking Out quest. When Captain Brass Hand Harry gives a broken hand, it can be "taken-apart" to form a few fingers. You pry the fingers from this hand. The rest is useless. The fingers are then combined with 4 other parts (thumb, brace, hand, and wrist), with a hammer and 2 bronze wires in the inventory, to smith a Brass hand. The Brass hand is subsequently used to gain the mark from the captain.