Battering ram and davy lamp: what they have in common

1. Step 1. Battering ram — works like — Pile driver. A battering ram and a pile driver both strike with a heavy weight: one breaks gates, the other drives piles.
2. Step 2. Pile driver — has part — Block and tackle. Lifting the weight.
3. Step 3. Block and tackle — has part — Rope. The rope runs around the pulleys.
4. Step 4. Rope — is made of — Plant fibre. Rope is twisted from plant fibres.
5. Step 5. Plant fibre — is material for — Wick. A wick is twisted from plant fibres.
6. Step 6. Wick — is part of — Davy lamp. A wick.

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