Maintenance should first check the tire pressure, wear, nut loose or fall off, remove the twins or tread on the inserts and nails and other sharp objects.

养护时首先应查看轮胎气压、磨损状况，螺母有无松动或掉落，除去双胎间或胎面上的嵌入物及铁钉等尖利杂物。

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Punch down any loose nails so that the floor is quite smooth.

把所有松动的钉子都钉进去，使地板平滑。

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Now this classroom was very old, and the blackboards, which had been nailed on to the walls with old black iron nails, had become loose over the years.

㗕上课的教室已十分破烂，黑板是用那些老式的黑铁钉钉在墙上的。经过这么多年，钉子已经松动了。

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