I want to ask about two scenarios in which people do this, and why they choose to do it. First, the arm bar. Traditionally, most of us are taught not to cross the feet. In BJJ this is typically a no-no. My instructors tell me that it causes the knees to spread apart, and I can see this. Lots of people get arm bars without crossing their feet, too, so it obviously works. But some very high level grapplers cross their feet for arm bars all the time. Robert Drysdale does it in the rolled up video. Ronda Rousey does it in MMA frequently. So there must be reasons for it. Since I already know the disadvantages, what are the advantages? Why would you choose to cross your feet, and how does it improve your arm bar? Second, when taking the back. I've seen a few people do this, as well. Of course there is the ankle lock open to your opponent, so that's one obvious reason not to do it. But I know that Ryan Hall is an advocate of crossing the feet during some of his back takes. I believe I've seen it a few times from Demian Maia, as well. So why do this instead of sinking both hooks in?