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An additional guard, member of a longpoint family.It has the shield extended forward, with the sword taking bind behind it (not in front of it as usual lonpoint would do). Possibly this position could be considered a late reaction to the thrust from tertia custodia. But it can also be a typical reaction to a thrust from vidilpoge.
It is not clear if I.33 shows this guard because it should be used, or because it is not recommended, but we should know it because the opponent may use it.