Okay, I'm new to the game. I've lurked and searched, but I can't quite find an answer. This is how I'm reading blocks (specifically evocation blocks, not blocks that block an action other than "attack") and defenses work (let's assume physical conflicts for simplicity):
First off, the most basic is a defense roll. It does not take an action and is done by the target in response to the attack roll. It uses a skill (Athletics, Weapons, or Fists, as appropriate, with Athletics being able to be used against all physical attacks).
The Full Defense action gives +2 to defense rolls.
Second would be a Block. This is an action set up by the character, an thus requires an action to be used. A Block is used to prevent an action. Thus, in this case, it would be preventing the attacker from attacking. However, when a character uses a block, they can't do anything else that turn (other than take supplemental actions, of course). A Block lasts until it is beaten, or until the beginning of the blocker's next turn. The advantage of a block is that it is in addition to the defense roll. Thus, the attack must beat the block and the defense roll.
An Evocation Block works similarly to a block in all ways except that its duration can be extended by allocating shifts to duration. Also, an evocation Block can be used to grant armor (half the shifts allocated for power). Armor doesn't go away if the character is hit (but does when the duration expires).
Finally, an Enchanted Item can have defensive effect in it. The character may expend the item's charge and use the item instead of a defense roll (or as armor, but not both unless two charges are expended).
Is this correct?