Corrugated fluting layer and railway semaphore: what they have in common

1. Step 1. Corrugated fluting layer — is part of — Cardboard box. A corrugated layer adds stiffness.
2. Step 2. Cardboard box — is made of — Wood pulp. Corrugated board.
3. Step 3. Wood pulp — is used in — Paper machine. The raw material.
4. Step 4. Paper machine — is made of — Cast iron. The rolls are cast iron.
5. Step 5. Cast iron — is material for — Railway semaphore. On a cast-iron mast.

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