Make sure the post is 'square' to the floor. [=make sure that there is a right angle where the post and the floor meet]
I'll go on the trip if I can 'square it with' my parents. [=if my parents will agree to let me go]
Here's the rest of the money. Now we're 'square'. [=now we don't owe each other anything]
(..) One more job and we're straight. Sound good? Oh... I was gonna wait until we were square, but what the hell. These are for you. Now give me your burner. I'm gonna need you behind the wheel again real soon. You call, I'm there. (..)2017 Baby Driver