紧要的环节vital link

紧要的时机crucial moment

• 说在节骨眼上

  hit the nail on the head

• 抓住工作中的节骨眼儿

  identify the most crucial part of one's work

• 现在正是在节骨眼上。

  We are at a critical juncture.

• 就在这节骨眼上，援兵开到了。

  Just at the vital moment, reinforcements arrived.