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This timber is used where the coal seam is separated by a rock band and
one bench is loaded out before the other. If the top bench is worked off
first, the jack posts are set between the bottom bench of the coal and the
roof. If the bottom bench is cleaned up first, the jack posts are set
between the bottom and the top bench. At least two jack posts should be
used and as many more as is necessary to keep the top bench of coal or the
roof from coming down while the coal is being loaded out. Kentucky
Source:
Dictionary of Mining, Mineral, and Related Terms
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