Lure the enemy with counterfeits. Punish the callow youth.

The expression comes from a story about two poets in the Tang Dynasty. Once, a celebrated poet named Zhao Xia was about to visit Suzhou, the city of gardens in south China. When the poet Chang Jian heard about this, he knew that Zhao was sure to stop by the Lingyan Temple (Temple of Intelligent Rock). So he went there at once and wrote two lines of poetry on the wall. When Zhao Xia arrived and saw the two lines left by Chang, he wrote two more lines, completing the poem. It is generally agreed that the last two lines are far superior to the original lines of Chang Jian. Therefore Chang Jian is said to have “cast a brick to attract jade.” Today, the expression is still used by people who want to sound modest. For example, a person who is asked to speak first at a meeting might say, by way of modesty, that he is going to “Cast a brick to attract jade.”