knock the stuffing out of

beat the stuffing out of

To beat very severely.

don't knock yourself out

Don't overexert yourself (in doing something that does not require much effort).

knock down a peg

Synonym of take down a notch.

knock for a loop

To astonish; to stagger or overwhelm; to confuse or disorient.

knock it off

to tell someone to stop doing something annoying or wrong.

knock on heaven's door

To die or be close to death.

knock on wood

To take a customary action to ward off some misfortune that is believed to be attracted by a presumptuous statement.

knock oneself out

To go ahead; to do as one pleases; to enjoy oneself; to endeavor very hard at a task.