Scissors and submarine: what they have in common

1. Step 1. Scissors — uses — Wedge. The blades cut like wedges.
2. Step 2. Wedge — is used in — Icebreaker. The bow rides up onto the ice and crushes it.
3. Step 3. Icebreaker — has part — Propeller. Propellers.
4. Step 4. Propeller — is part of — Submarine. A propeller.

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