A phrase often used towards someone who states the obvious.

When someone says something that is very obvious

A Saying That People Say When Someone States The Obvious

This means "obviously" but you say this if u wanna be sarcastic.

A snide response to someone (usually a know it all) who has made a statement that is very obvious using a sarcastic reference to Sherlock Holmes the famous literary detective.

What you say to know-it-alls when they're being dumbasses.

Someone who believes they always have the answers, a know-it-all. Usually used to insult that person when they make a stupid insight or just repeat what has already been said. Sherlock being a reference to the literary detective sherlock Holmes.