Interlinked metal rings and vacuum pump: what they have in common

1. Step 1. Interlinked metal rings — is part of — Scissors. Finger rings.
2. Step 2. Scissors — is made of — Bronze. Ancient scissors were bronze.
3. Step 3. Bronze — is material for — Check valve. The valves of ancient pumps were bronze.
4. Step 4. Check valve — is part of — Vacuum pump. Valves stop air from flowing back.

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