clear like pointing at a palm be thoroughly familiar with know sth. like the palm of one´s hand know very well know what o´clock it is at one´s fingertips know sth like the palm of one´s hand know … like the palm of one´s own hand off pat have down pat know ... like the palm of one´s own hand as plain as pointing to one´s hand as plain as pointing to one´s hand
You need to become fully conversant with the company´s procedures.
你得对公司的程序了如指掌。
—— 给力词典精选She knows the layout of the back streets like the back of her hand.
她对那些偏僻的街道了如指掌。
—— 给力词典精选He knows the terrain of this locality like the back of his hand.
他对这一带的地形了如指掌。
—— 给力词典精选He has his Provensal legendary lore at his fingers´ends.
他对普罗旺斯地区的口头传说了如指掌。
—— 辞典例句´We know all about you,´ she said disdainfully.
“我们对你了如指掌,”她轻蔑的说。
—— 《柯林斯英汉双解大词典》