Once upon a time, a bird-catcher enjoyed casting nets to catch birds.
One day, seeing birds about to fly by, he immediately cast his net and waited patiently.
Soon, a bird arrived as expected and was caught at once.
Drawing in the net, the bird-catcher found the bird trapped in a single mesh. He thought, "If one mesh is enough, why have more?" So, he specially made a net with only one mesh, cast it in the same spot, and waited eagerly.
However, he never caught another bird thereafter.