Another ABG question

Working on going over material for upcoming class and exam next week on ABGs and was hoping that someone might be able to either direct me to a previous post or explain. Did a search on here the other day and had pulled up a post from a couple of years ago with explanations of ABGs from Esme and Grntea. I had glanced at the info and bookmarked it because wanted to go back to it, of course now I can't find it in my bookmarks. Grntea had a way of explaining it that I wanted to look further into, not completely sure if it was the tic tac toe method that I have seen in a couple of posts. If anyone knows about the method that I am talking about and could post an explanation of it or a link to the post it would be greatly appreciated. Thanks.