cob and snap

For cob you turn a form into panhellenic, that form will be distributed to the sororities participating and if any are interested they will invite you to an informal recruitment party and then invite you back to present you a bid or they ghost you.

Snap bids only happen before bids are handed out on bid day. Girls who were released from all houses before pref round but who had ranked every house and accepted every invitation are eligible for a snap bid and they run to their house with everyone else. Houses who did not match enough girls to get to quota may offer snap bids and that makes them very, very rare at Alabama. Do not get your hopes up for a snap bid.
If you are interested in COB you may fill out the panhellenic form, you may also reach out to the houses you are interested in and tell them you are interested and it really helps to have friends in the chapter to make this work. COB is not run by panhellenic; it is each house on their own deciding to COB or not. Houses at or above quota can not COB.

which houses typically participate in COB?