To tighten the connections or correct the angles in a construction project, since squares are made of right angles at exactly ninety degrees, which is the majority of building connections and materials.
To confirm plans and reservations, straighten, or organize.
"If this drywall's gonna hang right, you better square up that door frame."
"I got my vacation all squared up."
"It's supposed to be in the seventies this weekend, so I'm gonna get the lawn squared up."