(To) Cross All Your T’s And Dot All Your I’s

What does the idiom “(To) Cross All Your T’s And Dot All Your I’s” mean?

Definition:

To take care of every detail, including the minor ones

For example:

“Make sure your presentation is ready to go tomorrow. I want you to cross all your T’s and dot all your I’s. “

Notes:

This is also heard as “cross every T and dot every I.”