撿漏

捡漏
jiǎnlòu
  1. to repair a leaky roof
  2. (dialect) to find fault; to nitpick
  3. (slang) to score a bargain (esp. when the seller is unaware of the item's true value)
  4. (slang) to take advantage of an unexpected opportunity

CEDICT

dialect slang

Entry Composition

1 撿 jiǎn to pick up; to collect; to gather
2 漏 lòu
  1. to leak
  2. to divulge
  3. to leave out by mistake
  4. waterclock or hourglass (old)