It interrupts our logical analytic discursive thinking. That's the beginning of don't know. He saw the essential nature of things. In Zen talk, the stick is symbolic of or represents our true nature, our essential nature. We also have in common this way - seeking mind.
Nobody is here by accident.
All of us are here together out of some question, some wonderment, and this is our ancestor who is saying to us, if you have a Zen stick, if you have essential nature, if you have true nature, I will give you a Zen stick, I will give you a good beating. If you don't have true nature, if you have emptiness, everything is blankness, or nirvana, I'll take it away from you. Life simply isn't that way. Our life is constant, moment by moment by moment by moment. So if you have a Zen stick, if you have essential nature, already you have lost your life.