Longwall mining.
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Previously:
https://www.homemadetools.net/forum/...393#post177413
https://www.homemadetools.net/forum/...748#post186505
https://www.homemadetools.net/forum/...610#post201388
https://www.homemadetools.net/forum/...694#post209644
https://www.homemadetools.net/forum/...296#post116284
