Hand cannon and plumbing: what they have in common

1. Step 1. Hand cannon — uses — Gunpowder. Gunpowder propels the projectile.
2. Step 2. Gunpowder — is used in — Grenade. An explosive.
3. Step 3. Grenade — is made of — Clay. Medieval grenades were ceramic vessels.
4. Step 4. Clay — is material for — Plumbing. Minoan plumbing used ceramic pipes.

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