User blog comment:WarrenWitch/Aura/@comment-3146930-20141028003251

The way I see Aura is more like a buffer, covering the entire body and constantly activating on some level. As seen with Ren and Cinder, a person can focus their Aura into a singular point for better defense, but this may leave the rest of their bodies more vulnerable.

Jaune actually makes a good example here. As seen in the forest, Pyrrha uses her skill in Aura control to unlock his (something he may have been able to do on his own, with time and training that is), but he has no skill in actually using it like the others. However looking at his fights with Cardin and later the Ursa Major, his scroll is able to measure his Aura levels. This suggests that despite Jaune apparently having a lot of Aura, he can only use a fraction of it until he learns to control it. This would explain how Cardin bruised him despite still have some Aura left when fighting the Ursa Major.

As far as what Aura can actually block, I think it depends on the type of attack. Attacks from sharp objects (swords, scythes, or claws) are much harder to block. This can be seen with Yang getting a strand of hair cut off when fighting the Ursa. This would also explain why Ruby always uses the back of her scythe to fight humans instead of using the sharp side.

However what Aura can actually block is very inconsistent from fight to fight. Yang during the food fight was launched outside the building before falling back inside later and just laughed. Later Roman's mech slammed her into a wall and then punched her out, but this only made her stronger. Neo gets about 3-4 hits on her before slamming her into the roof and this knocks her out. Ruby being taken out by the mooks I can understand, as she fell a great distance and her Aura could have been depleted. Also before with the car, she was tired from using her Semblance so she may not have been able to focus on her Aura.