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]
(..) would have to kill you, go up to Nikki's room, kill her, then wait for your husband to come home and kill him. That would be even, Vernita. That'd be about square. Look, if I could go back in a machine, I would. But I can't. All I can tell you is that I'm a different person now. (..)2003 Kill Bill: Vol. 1