Lie flat and let your knees bend.

平躺曲膝。

《牛津词典》

Now, this has to stop somewhere. I can start claiming that I can somehow bend my coordinates to a plane, any surface is flat.

现在必须得停一下了，之前说到的，可以通过把坐标系变换到某平面上，那些曲面都是平的。

youdao

It takes a few seconds to cut a flat part, but it may take several minutes to bend it. Balancing production like this isn't easy.

切割板材只要几秒钟，但是折弯却要几分钟，让不同工序生产节拍协调一致并不容易。

youdao