When the concave upper nut is tightened, the effect produced is exactly the same as that produced by a hammer driving in a wedge.
当上螺母的凹面与之锁紧时,其效果与用一个锤子敲进一楔子的效果完全相同。
It takes some time to get accustomed to swinging the hammer - it is a much different technique than driving nails!
需要花点时间来熟悉挥动力锤—它是一个不同于楔钉子的技术活!
A hammer is used for driving [to drive] in nails.
锤子是用来钉钉子的。
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