This is Posta Mezana Porta di Ferro (Middle Iron Gate guard) because it is in the middle. And it is a strong guard, but needs a long sword. She throws strong thrusts and forcefully beats the sword up and then back with a blow to the head or arms, and so returns to her guard. But it is called a gate because it is strong, and is a strong guard who hurts as it breaks without danger and coming to the close.
With Posta Mezana Porta di Ferro, your sword is aligned straight down the centreline to your opponent, with the point of the sword hovering just above the ground. Keep the elbows relaxed, but held close to the body. This posta is classed as one of the stable stances, and it is the direct association of the blade to the hips that makes it so.
Used across almost every chapter of armizare, there are easily transferable descriptions of this posta. It appears in both the Sword in armour and Pollaxe sections. It also appears in the Dagger and Spear on foot sections where its application is conceptually the same, but in practice comes off as something of a variant due to the polar extremes of the weapon lengths.
Defence from Posta Mezana Porta di Ferro mostly comes from a strong beat up and to the right, followed by a cut down along the same line. It is also very possible to flick the point up, allowing a heedless opponent to run onto it, or lunge easily into a thrust. Given the straight line opposition of such tactics, these are safer with a long sword.
In all of these regards, it performs very similarly to Posta Dente di Zenghiaro. You can think of them as wide and narrow versions of each other. Where Posta Dente di Zenghiaro emphasises the beat and cut, the direct line of Posta Mezana Porta di Ferro more stongly emphasis the thrust.