Kong-ans are like fishing hooks.
If your mind is not clear the baited hook will drop into the pool of your mind, all your thinking will appear and you will be swallowed by the hook and be caught by your thinking.
If you cut off all thinking and only go straight "don't know," then the hook drops into clear mind and comes out of clear mind.
You will perceive the correct situation in the kong-an and not touch the hook.