The Full Guard (完全ガード) is an item that first appears in Fire Emblem: Path of Radiance. It is held in the 'items' section of a character's inventory in Path Of Radiance. The Full Guard can be equipped to any character at any point so they can benefit from its effects.
The Full Guard negates any bonus damage an enemy unit can do to a character. For example, if a Pegasus Knight had the Full Guard equipped, and they were shot by an arrow; it would do a normal amount of damage. This applies to all weapon bonuses, such as Anti-Laguz weapons, anti-cavalry weapons, extra damage to laguz from the spells each is weak to, and so on.
This makes the item incredibly useful. Most people give it to a flying unit they like to use in combat as it increases their effectiveness, since bows and wind magic deal a lot less damage. The item also is useful when given to Laguz units, as there are a substantial amount of Laguz killing weapons. The applications of the item are endless as each individual character can benefit from it, although obviously it does help some more than others.
The Full Guard is grouped together with other guarding items that exist in Path Of Radiance. Such as the Beorcguard, Laguzguard, and other items that reduce damage or prevent other effects that act on a unit in battle. The Full Guard is considered one of the most useful of this group as it's effects remove a unit's basic weaknesses.
Only one available Full Guard item exists in the game. This means a player has to be decisive with whom he equips the Full Guard. In many cases the Full Guard can mean the difference between a unit dying, or walking away virtually unharmed, this is what makes it so incredibly useful.