Steel well casing and sickle: what they have in common

1. Step 1. Steel well casing — is part of — Oil well. Steel pipes line the borehole.
2. Step 2. Oil well — uses — Drilling rig. A well is drilled by a rig.
3. Step 3. Drilling rig — has part — Diesel engine. The drive.
4. Step 4. Diesel engine — is part of — Combine harvester. Self-propelled combines run on diesels.
5. Step 5. Combine harvester — evolved from — Sickle. The machine replaced reaping by hand.

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