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]
(..) Bugger me! Let him speak. I bring a message... ...from Nottingham. Our men are to be hung in the square at high noon. And my boy? The boy too. Ten men in all. The hangings are part of the celebration... (..)1991 Robin Hood: Prince of Thieves