Braulio explains how the spider guard is great for keeping an opponent's weight off of you when they are on their knees looking to apply pressure and pass your guard. He also shows what to do when you pull them forward using your foot on the biceps and they step up with their opposite leg preventing you from transitioning to x guard. When this occurs, he establishes a reverse de la riva type hook and attacks the kiss of the dragon sweep.
Links to other Parts:
Part 1,
Part 2