Lu Ban was supposed to be a consummate（至上的，完美的） carpenter in ancient times. It is said that he once carved a wooden phoenix（凤凰） that was so lifelike（逼真的） that it actually flew in the sky for three days. Thus it was considered the height of folly to show off one's skill with an axe in front of Lu Ban.

This idiom excoriates（批判） those who show off their slight accomplishments in front of experts.