Pao Zhuan Yin Yu (To Attract Jade by Laying Bricks)
During the Tang dynasty, there lived a man named Zhao Gu, who was a very talented poet. Zhao Gu's poems were so well-written that even famous poets of his time enjoyed reading them.
At that time, in a place called Wu, there lived a man named Chang Jian, who also liked to write poems. Chang Jian greatly admired Zhao Gu's literary talent, and longed to know him personally. One day, Chang Jian heard that Zhao Gu would be travelling to Wu. He knew that Zhao Gu would definitely go visit Ling Yan Temple during his trip, because this was a very famous place which everyone who came to Wu went to see. So Chang Jian went first to the temple, and on the wall which was set aside for guests' comments and ideas, wrote two lines of poem.
When Zhao Gu saw the two lines of poetry on the temple wall, he could not help adding another two lines, because Chinese poems are always composed of at least four lines. And so Chang Jian achieved his goal. He said, "My poem is a brick, and Zhao Gu's poem is jade, I layed a brick, and attracted jade!"
This idiom is now a polite expression often used when giving an opinion or delivering a speech. It means that what one is offering is somehow lacking, and one is in hopes that others will, seeing it, offer something that is better.