This has always been a difficult passage for me. Swanger’s translation takes liberties with the text, while Leoni’s doesn’t make much sense to me.
Transcription by Steven Reich
Accia il nemico qual colpo gli piace per offender te, che sei in guardia alta. Tu dei tre, o quattro fia te percoter l’orlo del Brocchero in su & in giu, cioè con il fendente & con il falso della spada, il che facendo ti ue nirai a render sicurissimo da qualunque offensiuo colpo.
W. Jherek Swanger Translation
The enemy makes some blow that pleases him, in order to offend you, who are in guardia alta. You must beat the rim of your buckler up and down, that is, [in response to] the fendente or the falso of his sword [respectively], doing which, you will come to render yourself safe from any offensive blow.
Tom Leoni’s Translation
No matter which of the attacks the opponents chooses while you are in Guardia Alta, hit the rim of your buckler with your sword three or four times up and down, using the fendente and the falso. By doing this, you will be most safe against any attack.
I’m including Google Translate because, not being a fencer, it is unbiased.
Accia the enemy what shot he likes to offend you, who are in high guard. You three, or four fia you percoter the rim of Brocchero in up & down, that is with the blow and with the false sword, which you doing ue Nirai to render very safe from any offensiuo blow.
Lately I’ve been experimenting with a new interpretation. The basic idea is this: your buckler only moves up and down, never side to side.
For blows that come from above or below, fendente or falso, this obviously works. But where it really helps is for blows that come from the sides. Normally a good way to defeat a bucklerist is to throw a wide blow to one side and, when he chases it, snap back to the other side which is now open.
Since under my new interpretation I’m not allowed to move the buckler sideways to parry, thus I can’t chase my opponent’s sword and create an opening for him to take advantage of.
What I can do instead is track my opponent with my buckler. By that I mean I can rotate my whole body such that the boss of my buckler is always facing his center of mass. And I do this whether or not he is attacking so that I’m always covered.
So far it has proven quite effective so I’m inclined to think that this is what Manciolino is trying to say (or at least closer than what I was doing before).