Stones from another mountain can be used to polish our own jade.
Tips
history
From 《诗经·小雅·鹤鸣》: 他山之石，可以为错 (later 可以攻玉) - stones from other mountains can be used to grind your own jade. The full phrase 他山之石，可以攻玉 is still quoted whole and is one of the oldest still-active idioms in Chinese, roughly 2,500 years old.
usage
Commonly seen in policy papers, academic writing, and editorials as the title of comparative studies. Positive - treats outside examples as valuable learning material. Often truncated to just 他山之石 with 可以攻玉 implied.
