老lǎo马mǎ识shí途tú

Literal: the old horse knows the way
Figurative: An experienced person knows the way; veterans' know-how is invaluable for solving problems.

Where does 老马识途 come from?

During the Spring and Autumn period, Duke Huan of Qi, accompanied by his minister Guan Zhong, led a campaign against the state of Guzhu. They set out in spring and returned in winter, and on the way back the army lost its way among the mountains, unable to find the road out. Guan Zhong proposed relying on the instinct of the old horses: "The wisdom of old horses can be put to use." They released several, and by following their tracks the army found the route again and was able to return home.

Source (出处): 《韩非子》

How is 老马识途 used? Two examples

这zhè条tiáo山shān路lù他tā走zǒu了le三sān十shí年nián，老lǎo马mǎ识shí途tú，跟gēn着zhe他tā准zhǔn没méi错cuò。
He's walked this mountain trail for thirty years; like an old horse that knows the way, follow him and you won't go wrong.
遇yù到dào这zhè种zhǒng棘jí手shǒu的de谈tán判pàn，还hái是shì请qǐng老lǎo张zhāng出chū马mǎ吧ba，老lǎo马mǎ识shí途tú。
For such a tricky negotiation, better let old Zhang handle it; an experienced hand knows the way.

In Wanyu, all 400 chengyu have audio on every sentence, and you can save them to your decks and review them with spaced repetition. Free.