A pass route on offense in which the downfield receiver runs straight for a short distance before turning straight toward the middle of the field and continuing the route. A square in is usually set up to push the defensive player back down the field until he commits to a direction, and then cutting inward. Ideally, this gives the quarterback an open receiver in the middle of the field. Square in routes are best against man-to-man defenses where the receivers can get the defensive backs off balance.
The square in route is one of the basic pass routes used in passing offenses. While it generally looks like a 90-degree turn when drawn on paper, the route actually calls for the wide receiver to misdirect the defensive back before making the turn. Ideally, the defensive back will commit to the straight part of the route and turn downfield before the receiver turns, allowing him to run free across the middle of the field. Square in routes are less effective against zone defenses because there is often another defensive player guarding the center of the field, thus eliminating the advantage of the route.