了如指掌

1. 了如指掌 (liǎorúzhǐzhǎng)

   1. 形容对情况极为清楚 have sth.at one’s fingertips; know as one know his ten fingers; know like a book; know as well as a beggar knows his bag
      • 对他们的活动,他完全了如指掌

了如指掌是成语。

了如指掌 (liǎo rú zhǐ zhǎng)

1. 比喻對事情了解得非常清楚。