This is Posta Dente di Zenghiaro (Boars Tusk Guard), because the wild boar uses this method to strike. It makes great underhanded thrusts into the face without stepping through, and returns with a downward cut to the arms. And sometimes it thrusts to the face and it goes with the point high, and in thrusting, steps forward with the front foot, immediately returning with a cut to the head or arms, then returns to this guard and immediately makes another thrust with an advance of the foot. Also it defends against the narrow plays.
Posta Dente di Zenghiaro is one of the stable guards. The sword is firmly connected to the core and driven directly by the hips. This is a forward weighted stance. A line from the toes of the right foot to the point of the sword form the base of a long isosceles triange, with the left foot forming the triangles apex. When delivering a mandritto fendente cut, you should stop at or pass through this posta.
As the description makes very clear, by driving the left hip forward, the sword will deliver a powerful upward thrust or false edge cut. Delivering these while keeping the feet in place gives a fairly short range technique. Lunging forward with the right foot on delivery will obviously increase the range.
Regardless of whether you lunge or not, you will be perfectly placed to make a return cut along the same diagonal line, returning to your starting point, ready to repeat the pattern. The double motion of up and back along the same line gives a very short fast delivery. This is ideal for use in the narrow play, either as an attack or a defensive beat.