Letter slot and hydraulic press: what they have in common

1. Step 1. Letter slot — is part of — Letter box. A slot protected from rain.
2. Step 2. Letter box — uses — Postal service. The post.
3. Step 3. Postal service — includes — Pneumatic tube. The post.
4. Step 4. Pneumatic tube — has part — Capsule. A container for letters.
5. Step 5. Capsule — works like — Tablet (medicine). Dosage forms.
6. Step 6. Tablet (medicine) — uses — Hydraulic press. Tablets are pressed.

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