cob

I know someone just posted about COB but I had a different experience rushing and nobody I talk to seems to understand how COB works?
I'm a slightly older (21) transfer student but I will be here for four years. I did get dropped from rush right after Sisterhood round (I only had one house left that I wasnt in love with and it probably showed which is entirely my fault I know) and I registered for COB but I was wondering if anyone knew more about it? The houses that typically participate? How it works? Everyone I've asked says is starts in the spring semester is that also accurate? Who do they typically look for?