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]
(..) Somerset. How you doing? Didn't expect a menage-a-trois. It's not a problem. Sit down. Only for you do I do this, so it's a big risk. - So we're in this fair and square. - It's a deal. About an hour. Yep. Help yourself. That was money well spent. Yeah. (..)1995 Se7en