)Let me try to define this expression ! "Ca poutre" would litteraly correspond to "It beams". But "beam" being the verb applied to the word "beam", the wood part of many houses.
So, imagine you have a wooden beam. You take it, you throw it in somebody's face, and there you go, It BEAMS ! Right in his (or her) face !!
So, saying "Ca poutre" means more or less "It Rocks !", or "It rules", but with the metaphore of a wood beam, which is a bit more hardcore
