A four-man line can be shifted to anticipate the point of attack. Shifting can be very effective, but also weakens another part of the line. In PSF, the only formations which can’t be shifted are the 3-4 and Prevent.
PSF supports six types of shifts. Note that Over, Under, Tight, and Wide are used to improve defending against runs, while Stunts are used to increase pass rushing.
The Normal shift is the standard setup, neither stronger nor weaker against either side. The linemen line up directly in front of the offensive blockers.
In Over, the line shifts to the strong side (usually the offense’s right side). Better for defending against runs to their right (your left), weaker on the left side.
Shifting Under is the opposite of Over, used if you expect them to run to their weak side (their left). Like Over, it places a lineman directly over the center.
In the Tight shift, the defensive linemen line up on the blockers’ inside shoulders, thereby cheating inside to defend against Middle runs. Much weaker against outside runs.
In the Wide shift, the defensive linemen line up on the blockers’ outside shoulders to defend better against outside runs. Much weaker against middle runs.
Stunting is different from all the other line shifts. Rather than improving run defense, Stunting increases your pass rush (and gives up more rushing yards). Use only in Pass Defense.