Semaphore arm and parachute: what they have in common

1. Step 1. Semaphore arm — is part of — Railway semaphore. The position of the arm is the signal.
2. Step 2. Railway semaphore — uses — Lever. The semaphore is set by a lever.
3. Step 3. Lever — is used in — Umbrella. The folding mechanism is levers.
4. Step 4. Umbrella — is made of — Silk. The canopy is made of silk.
5. Step 5. Silk — is material for — Parachute. The canopy is silk.

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