Please open the train [car] window a bit [crack; fraction].

请把这车窗打开一点点。

《新英汉大辞典》

When it reaches a crack, the sealant is sucked out of the train and into the crack in the same way that water is lost.

遇到裂缝时，装置就会挤出密封剂，这种方式与水从缝隙漏出一样。

youdao

Who made me train until my bones crack?

是谁训练我直到骨裂筋断？

youdao

So the community fought back: a disciple of a local Shinto priest was called in to train a crack team of wrestling coaches, and Kosaka organized a sumo club that wouldn't contravene the Education Ministry rulebook.

CNN: Wrestle Mania

In the meantime, businesses need to keep empowering each of their employees to crack their engagement code so we can get this train out of the station.

FORBES: The Engagement Frenzy!

We have a laugh, we have a crack but when it's time to get down to business we get down and train hard -and that's all down to Rob.

BBC: Great Britain amateur boxers praise coach Rob McCracken