Here is a look at your typical Power O blocking scheme from an I-formation. The two keys are the kick out block by the first back (a U-back or a FB, here, a FB) and the pulling opposite ("O") guard to the playside hole.
Believe it or not, the inverted veer is really a Power O blocking play. Many know that you can run the same blocking scheme with the inverted veer up front, down to the pulling guard, but it works because the "kick out" block is accomplished by kicking out the DE by optioning off of him. Literally, just like you'd run power, if the DE stays out then he's blocked out (nominally, if there is indecision in the inverted veer, the QB keeps).