Chisel blade and tunnelling shield: what they have in common

1. Step 1. Chisel blade — is part of — Chisel. A sharpened steel plate.
2. Step 2. Chisel — is used in — Tunnel. Hezekiah’s Tunnel was cut by hand with chisels.
3. Step 3. Tunnel — uses — Tunnelling shield. Shield tunnelling.

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