This is Posta Frontale (Forehead Guard), called by some masters Posta Corona (Crown Guard), which for crossing blades is good and for thrusts is also good. Also if the thrust is high, she crosses swords and passes off the line. And if the thrust is too low, she also goes off the line and beats its point to the ground. Also you can do otherwise, in that striking with the point return with the back foot and strike with a downward cut for the head or arms, then move to Posta Dente di Zenghiaro and immediately throw a thrust or two while advancing the foot and return with a downward cut to that guard.
Posta Frontale is more of a transition point than a position you would hold. From a separate chambered posta, you will arrive here typically after beating aside an incoming attack. Less frequently, you might also use it to sweep aside your opponents weapon to initiate an attack of your own. As it is drawn, you would come to this position from a posta which is chambered on the right. You could also just as easily move from a sinistral posta to posta frontale. The mechanics would be essentially the same, except you would end with your right foot forward instead.
From your starting posta, drop your elbows close to your ribs. Ideally, they should be no more than a handspan from your body. Extending your elbows will weaken the structure, however, the circumstances you are facing may demand this to a certain extent. How you hold the forearms determines the height of the sweep you are making. The illustration shows the hands held quite high. In other examples throughout the book, the hands are held almost as low as the knees. Keep the blade upright, but with the point tipping somewhat forward.
You want to move your hands in something of a horizontal circle. Catch your opponents blade at the furthest point with the flat of your blade. Your own blade will sweep across your body completely, brushing your opponents blade offline. As you lock your arms and sword in place, they will trace back slightly along an arc. Your sword will naturally twist along its axis, flicking your opponents weapon to the side. When done properly, it will have a soft quality to it. It is more a scoop than a beat. This is the moment pictured.
From here, you can step forward, making an exchange of thrusts. You can also continue the momentum downwards, breaking the thrust.
Fiores last suggestion is a combination set. Exchange the thrust, which will leave you in posta longa. From there, follow up with a fendente cut to posta dente di zenghiaro. Continue with a second thrust and cut combination from there, returning again to posta dente di zenghiaro.