The goal with the 2-2-1 press at it’s core is to force the ball to the sidelines and keep it there. Ideally, this will give players a chance to trap in one of our three hot zones : the baseline-sideline corner and the halfcourt sideline corner, whether before or after they cross halfcourt.
Figure

There are three levels to the 2-2-1 – the front, middle, and back. The front will usually be your two most agile defenders, generally your point guard and shooting guard. They will start on the elbows. The back line is reserved for your slowest defender, who will play safety at the back. The middle line will likely be for your power forward and small forward line up, with the length to disrupt passes while still possessing the footspeed to recover back if need be.