Panel building and sickle: what they have in common

1. Step 1. Panel building — has part — Elevator. Lifts.
2. Step 2. Elevator — has part — Pulley. The rope runs over a pulley.
3. Step 3. Pulley — is part of — Belt drive. The belt wraps around pulleys.
4. Step 4. Belt drive — is part of — Combine harvester. Belt drives.
5. Step 5. Combine harvester — evolved from — Sickle. The machine replaced reaping by hand.

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