Pit prop

A pit prop or mine prop (British and American usage, respectively) is a length of lumber used to prop up the roofs of tunnels in coal mines.

Canada traditionally supplied pit props to the British market. As coal mining declined in importance and metal supports were used, the term became infrequently used.

单词	Mine prop
释义	Mine prop 英语百科 Pit prop A pit prop or mine prop (British and American usage, respectively) is a length of lumber used to prop up the roofs of tunnels in coal mines. Canada traditionally supplied pit props to the British market. As coal mining declined in importance and metal supports were used, the term became infrequently used.
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Mine prop

Pit prop