knock down a peg

don't knock yourself out

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

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.

knock out

To strike or render unconscious

knock out of the box

To cause something to be replaced by something else.