Barbed harpoon head and oil well: what they have in common

1. Step 1. Barbed harpoon head — is part of — Harpoon. Barbs keep the prey from slipping off.
2. Step 2. Harpoon — has part — Rope. A line connects the head to the hunter.
3. Step 3. Rope — is part of — Block and tackle. The rope runs around the pulleys.
4. Step 4. Block and tackle — is part of — Drilling rig. The block and tackle lifts the drill string.
5. Step 5. Drilling rig — is used in — Oil well. A well is drilled by a rig.

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