見縫插針 [见缝－针]

Jyutping gin3 fung6 caap3 zam1
Pinyin jiàn fèng chā zhēn

Definitions (CC-CEDICT)
  1. lit. to see a gap and stick in a needle (idiom); fig. to make use of every second and every inch
Definitions (Wiktionary)
  1. phrase, idiomatic
    to make use of every bit of available time or space