捡漏
jiǎn​lòu

nitpick

捡漏 (撿漏) jiǎn​lòu
nitpick verb
to find fault or nitpick (dialectal usage)
repair roof
to repair a leaky roof
score bargain
to purchase a valuable item at a low price, especially when the seller is unaware of its true value (antiques slang)
seize opportunity
to take advantage of an unexpected opportunity or someone else's mistake

Sources
Definitions
CC-CEDICT