A sharp tool, or bit, was hung from a rope and jerked up and down by men jumping on a spring-board.

粗绳子上挂着锐利的工具，即钻头，由踏板上跳跃的人把它拉起又放下。

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A sharp tool, or bit, was hung from a rope and jerked up and down by men jumping on a spring-board.

粗绳子上挂着锐利的工具，即钻头，由踏板上跳跃的人把它拉起又放下。

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