（解説文要約）
ニナワセとは、切羽の運搬路に作る支柱です。
天井にハリをあて、両端に柱を打ち込みます。
後山が石炭を運ぶ際に背中をこすらないように、ハリには細い木を使用していました。
通常はクサビを使わないので、両端の柱の寸法を正確に決めることがコツでした。
This illustration shows pillars called "Ninawase" which were made in coalface driveways.
First, a beam was attached to the ceiling and pillars were inserted on both ends to support the beam.
Since wedges were not used for Ninawase, the size of the pillars had to be accurate.
Thin props were used as beams so that "Atoyama" helpers would not scratch their backs while loading out coal.