Pivot joint and refrigerator: what they have in common

1. Step 1. Pivot joint — is part of — Blacksmith’s tongs. The pivot of the halves.
2. Step 2. Blacksmith’s tongs — is used in — Forge. The smith holds the workpiece with tongs.
3. Step 3. Forge — uses — Combustion. Metal is heated in the flame.
4. Step 4. Combustion — is used in — Incubator. They were heated by fire.
5. Step 5. Incubator — has part — Thermostat. Keeping the temperature.
6. Step 6. Thermostat — is part of — Refrigerator. A thermostat.

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