表达 “know something inside out” 的意思是 “对某件事情、某个科目或主题了如指掌、洞悉透彻”。

• Don’t worry! You’ll be fine in tomorrow’s exam. You know the book inside out by now!
  别担心！明天的考试你一定会考好的。你现在对这本书已经了如指掌了！
• If you ever have any questions about the new IT system, ask Polly. She helped build it, so she knows it inside out.
  如果你对新的信息技术系统有任何疑问，就去问波莉吧。这个系统是她帮忙建立的，所以她对整个系统了如指掌。
• My grandad was a chess fanatic. You could ask him anything – he knew the game inside out.
  我祖父曾是个国际象棋迷。你可以问他任何问题，他对这个游戏了如指掌。