Rifle magazine and refrigerator: what they have in common

1. Step 1. Rifle magazine — is part of — Assault rifle. A detachable magazine.
2. Step 2. Assault rifle — has part — Spring. A return spring.
3. Step 3. Spring — is part of — Bogie. Spring suspension.
4. Step 4. Bogie — is part of — Refrigerator car. Bogies.
5. Step 5. Refrigerator car — uses — Ice house. At first — ice.
6. Step 6. Ice house — evolved into — Refrigerator. The refrigerator replaced natural ice.

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