Beginning with Yu the Great, the Xia Dynasty had lasted about 400 years before Jie became the supreme ruler.
And that was in the 18th century BC. Jie was extremely tyrannical and dissolute. This aroused great resentment among the people. Tang, the chief of the tribe Shang, took advantage of this situation to overthrow the Xia Dynasty and establish the Shang Dynasty in the early 17th century BC. During his preparations for the overthrow, Tang won popular support.
One day, Tang was having a walk in the open country. He saw a man catching birds with a big net spread like a cage and mumbling: "Come on, birds! Come into my net. All of you, whether flying high or low, east or west, just come into my net!"
Tang walked over and said to the man: "This method is ruthless! You'll spare no birds this way!"
With these words, he cut the net down on three sides. Then he murmured in a light voice as if praying: "Oh, birds! Fly to the left or right as you like. And if you're really tired of your life, come into this net!"
When chiefs of other tribes heard about this, they were all moved. They said: "Tang is a good king indeed. He is so kind even to birds and animals. He must be more merciful to human beings." And very soon, more than 40 tribes pledged allegiance to Tang.
From that story came the idiom "wăng kāi sān miàn," meaning "to leave three sides of the net open." Later, people changed it into "wăng kāi yī miàn," that is, "to use only one side of the net (since the other three sides are left open)." It tells people to give somebody a way out and to be lenient or merciful.
wăng kāi yī miàn
chē shuǐ mă lóng
endless stream of horses and carriages – heavy traffic