Street light and needle: what they have in common

1. Step 1. Street light — is part of — Tunnel. Lighting.
2. Step 2. Tunnel — uses — Rock drill. Driving the Mont Cenis tunnel.
3. Step 3. Rock drill — has part — Piston. A percussion piston.
4. Step 4. Piston — is part of — Syringe. A plunger.
5. Step 5. Syringe — has part — Needle. A hollow needle.

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