弄斧班门 — “To show off one's meager skill before an expert”

During the Tang Dynasty, Li Bai, known as the 'Immortal Poet,' is said to have drowned after falling into a river while drunk, and was buried at Caishiji on Niuzhu Mountain in Dangtu. Many literati and poets of later generations composed verses there to mourn him.

The Ming Dynasty poet Mei Zhihuan, showing self-awareness, wrote a poem that included the lines: 'A mound of earth by Caishi River, Li Bai's poetic brilliance shines through the ages. Visitors come and go, penning a few lines, like dropping a big axe before Lu Ban's gate.' These lines humorously suggest that compared to Li Bai's genius, their own poetic attempts were insignificant, much like showing off rudimentary skills in front of a master craftsman like Lu Ban, thus giving rise to the idiom.