Punched rod hole and bellows: what they have in common

1. Step 1. Punched rod hole — is part of — Index card. It holds the cards in the drawer.
2. Step 2. Index card — is made of — Paper. Paper.
3. Step 3. Paper — is material for — Player piano. The program is a perforated paper roll.
4. Step 4. Player piano — has part — Bellows. Pedal bellows create suction.

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