This is an optional sub-system for Glory Road combat. It is optional because it adds a layer of complexity to an already-complex combat system. When I was ready to publish the full game rules, I realized that the targeting and armor avoidance system we had used over the years was too complex and had largely fallen into disuse, although it was quite popular with some, a sizeable minority, of the players. This is a much simpler system, although it is still not simple.
It does, however, have its advantages. It often makes combat quicker. Using the sub-system may make one round of combat more complex but it can reduce the number of combat rounds. It gives the combatants more meaningful options. If the player-characters use it and their foes do not, it can give the PCs a unique advantage. I admit that I am a meanie and the NPC foes of my characters will use these options but they don't use them as often as the PCs.

https://www.drivethrurpg.com/product/337007/Targeting-and-Armor-Avoidance-2-ed?manufacturers_id=11833