know the drill

as you know

as it is already known.

drill down

To examine information at another level or in greater detail; especially in a database, to navigate to a more detailed level or record.

fire drill

Any pointless, unproductive, useless, or chaotic activity.

fuck if I know

I have no idea whatsoever

hell if I know

Synonym of I don't know.

I don't know about that

I am not sure that I agree; expressing doubt or skepticism.

I hardly know her

A joking retort that draws attention to the possibility of sexual innuendo when a word ends with a schwar.

it takes one to know one

Expressing the same underlying character-judgment themes as pot calling the kettle black or set a thief to catch a thief.