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。

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"Pets that are out of their comfort zones can have behavior problems in the car, which can be dangerous while driving, " says Hammer.

CNN: Tips for road tripping with pets

Finch Foundry is a traditional 19th Century working forge powered by three water wheels driving a huge tilt hammer and grindstone and has been owned by the National Trust since 1994.

BBC: Devon - Get fired up at foundry day