Managed to get this ring in an adventure as loot. Was curious as to how it functioned. According the book:
Ring of Force Shield:
An iron band, this simple ring generates a shield-sized (and shield-shaped) wall of force that stays with the ring and can be wielded by the wearer as if it were a heavy shield (+2 AC). This special creation has no armor check penalty or arcane spell failure chance since it is weightless and encumbrance-free. It can be activated and deactivated at will as a free action.
From what I'm gathering, its usable for Wizards and Sorcerer's without any problems to spell casting. Essentially getting a +2 AC 'Force-effect' shield that you can activate at will. I know that the MB can be enchanted and the like. Was just curious as how people use it. I figure you can have it off while your doing something, and then activated afterwards, getting the bonus.
If that were the case, could you give it to a character using a two-handed weapon and allow them to activate it after they attack, giving them some bonus AC that they're lacking by not having a shield?