With Usurper 2 just out, the obvious post for today is a few examples of how things work. 

Let us say our intrepid hero Bimf the Barbarian is planning to do some prime looting, however his considerable ambition is blocked by a locked door in his path. 

Bimf have had it explained to him that battering down doors, while satisfying, makes noise and he is not confident he can fight off all 238 guards that patrol this fortress. So lock picking it is.

The GM decides that picking a lock is well within the possibilities of what Bimf can accomplish and so an Action / Event roll is made. Let's roll 3 times and see how you can interpret various results. 

My first roll is a 91 which is "Success and discovery" 

 Not only does Bimf succeed in this case, but in the process he learns something interesting or useful. The GM might give Bimf's player some information on the guard schedules (so he can dodge them later) or tell him that while he works on the lock, he notices that a lot of the statues in the courtyard look an awful lot like common people from the village but in stone and isn't it weird how their faces are all contorted in fear?

The second roll is a 17, "Failure". 

Bimf did not manage to get what he wanted. Failures cannot be attempted again unless the table says you can do so. In this case, no amount of messing with the lock picks will get Bimf through this door. This is where the Traits come in. If Bimf has a suitable Trait like LOCKPICKING or perhaps ROGUE or even REALLY QUITE CLEVER if the GM is feeling generous, he can "burn" that Trait and roll again. 

The player of Bimf will of course have to narrate how he applies that quality to overcome the obstacle. 

The third is 78, "Success". 

Easy enough: The characters get what they were trying to get out of the situation. In this case the door has been picked and Bimf can proceed to loot the temple (which is certainly not going to be filled with evil monsters). 

What happens if the lock is really high quality? (most medieval locks were not) The GM might rule that this is not possible to a normal person. In this case, Bimf could burn a relevant trait to get an attempt. If as above, he has a trait for ROGUE, the player can burn that to allow a roll. After all a normal person can't pick this master-crafted lock but surely a rogue can do just such a thing. 

This sort of thing is called a Condition and Conditions can also be met in different ways. If the Condition is that the lock is master-crafted, one way to negate the Condition might be to have someone forge you some keys or find a master-crafted set of lockpicks. 

Conditions work best if the GM is open ended in setting up the situation and scenario. It is okay to have some ideas in mind about how it can be solved, but be open to the players suggestions as well.