Editing Unwritten: System Reference Document/Aspects and Fate Points (section)

===Promoting Boosts===

Sometimes when you’re creating a new aspect, you find that there’s a boost in play that’s exactly the aspect you want to make, turning a momentary benefit into a lasting one. Great! That’s called promoting a boost. Just declare an aspect you’re making to have the same name as a boost in play, and you’re done. If the action gives this new aspect a free invocation, it has two instead thanks to the boost being active. If you haven’t named the boost yet, now’s the time to do it.

For example, say I am trying to wrestle a Book from your grasp and get a boost from that Oppose action, and we say that you managed to get me A Little Off-Balance. On your next action, you follow-up by saying that you want to keep me off-balance by creating an advantage. You roll for the advantage, succeed without needing to use the boost, and then name the advantage A Little Off-Balance with two free invocations (or three if you succeeded with style—essentially one extra free invocation).

Even if you’ve used a boost already, nothing says you can’t bring that idea back around as an aspect later in the scene if it’s appropriate. There’s no special rule about that, just something to keep in mind. In our example above, you could still create the A Little Off-Balance advantage, even if you use the boost on that roll or on a past turn.