平巷頂板背板
Astel \As"tel\ ([a^]s"t[~e]l), n. [OE. astelle piece of wood, OF. astele splinter, shaving, F. attelle, astelle: cf. L. astula, dim. of assis board.] (Mining) An arch, or ceiling, of boards, placed over the men's heads in a mine.
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