瞭如指掌

了如指掌
liǎorúzhǐzhǎng
variant of 了如指掌 liǎorúzhǐzhǎng

CEDICT

to know like the back of one's hand

Wiktionary

本指天下事如掌中物，易於了解。語本《論語．八佾》：「『知其說者之於天下也，其如示諸斯乎？』指其掌。」後比喻對事情了解得非常清楚。《蕩寇志．第三三回》：「雖未出兵打仗，而戰陣攻取之法，瞭如指掌。」也作「了如指掌」、「了若指掌」、「瞭若指掌」。

重編國語辭典

對情況非常清楚、了解

維基詞典

Homographs

了如指掌 liǎorúzhǐzhǎng
  1. to know sth like the back of one's hand (idiom)
  2. to know (a person, a place etc) inside out

Entry Composition

1 瞭 liǎo
  1. (of eyes) bright
  2. clear-sighted
  3. to understand clearly
2 如 rú
  1. as
  2. as if
  3. such as
3 指 zhǐ
  1. finger
  2. to point at or to
  3. to indicate or refer to
  4. to depend on
  5. to count on
  6. (of hair) to stand on end
4 掌 zhǎng
  1. palm of the hand
  2. sole of the foot
  3. paw
  4. horseshoe
  5. to slap
  6. to hold in one's hand
  7. to wield