lit. repair the plank road by day while secretly crossing the Wei River 渭河[Wèi Hé] at Chencang (idiom, refers to a stratagem used by Liu Bang 劉邦|刘邦[Liú Bāng] in 206 BC against Xiang Yu 項羽|项羽[Xiàng Yǔ] of Chu)

fig. to feign one thing while doing another

to cheat under cover of a diversion