Alright friends, I wanna talk about doors. Specifically doors of the locked variety. We have seen several of them this season in particular, and it always seems to be Sam who finds himself on the other side.
In 10x03 and 10x07 Sam found himself in positions of needing to lock monsters behind doors to keep them from attacking. He tried his hardest to get through to them but was unsuccessful both times. The doors, however, eventually did open. Dean chopped his down with a hammer, while Elle never made it out of hers alive.
Again in 10x10 we find Sam with another locked door, only this time it is he who is locked out and trying with everything he has to get to Dean on the other side. As was the case with trying to get through to demon!Dean and Elle, he is unsuccessful in breaking down the door. I wonder how long he would have stood there kicking before trying to find the proper tool to break down it down? He knows what needs to be done, but the methods he applies are all wrong…
Let us then appreciate the significance of Cas, who once upon a time last season needed Sam’s assistance with getting through a door because he didn’t have the words required to solve Metatron’s riddle, being the one who does have the necessary tools this time to get through to Dean. He uses his grace, his precious, fading grace to blast through the door without hesitation.
I’m not saying this is incredibly important symbolism that is going to come into play later on but… no wait that’s exactly what I’m saying.