"What are we going to do with this leaky hosepipe?", " I know ! let's use it as a garden sprinkler!"

You know, I'm not really sure what to do next.

The clandestine operations were only known to a select few, those in the know were sworn to utmost secrecy.

I should know better than to eat junk food every day.

I hope we get to know each other better.

He appeared from who knows where.

Now I know how to solve the problem.

Before you know it, the weekend will be over.

Don't you know how to swim?

You know the drill.