How to Do an X-Pass in BJJ
The X-pass in BJJ is really just an advanced version of the toreando ("bull fighter") pass, but like most innovations on existing techniques in jiu jitsu, it works against a much more educated range of competitor. We'll take a look at what has now become the "classic" X-pass, then take a quick look at a simple variation that works extremely well against reverse De La Riva guard (RDLR) and other types of hooks. The name "X-pass" comes from the crisscross motion you're making with your arms (and with your partner's legs in relation to their upper body positioning).
The Set Up
Starting from inside your partner's butterfly guard, pop up to your feet so that you are in a "sumo squat" position of sorts. It's not necessary to stand all the way up initially, but this pass will also work from the feet if you get the right reaction from your partner. Next up, you're looking for three points of contact. First, your left hand will go outside of your partner's right knee. Second, your right hand will "karate chop" your partner's left hip, getting the coveted inside control. Be sure both elbows are in really close to your body here, unless you enjoy being Kimura'd or having your partner pummel inside for control. Third, your head will drive into your partner's neck or upper chest (note: be sure to keep your back straight during this part). Now you can start to drive your partner's back to the mat. If you don't get any response, just hop around their guard; however, it's extremely likely that your partner will try to engage you with their legs. This is where the "X pass" portion of this toreando comes in to play.
Now that you're starting to flatten your partner, they are doubtless going to try to reach out and hook your leg. Here's the important thing for this pass: your leg cannot be there for them to hook. As you flatten your partner out, the idea is to turn them like a steering wheel, so that they start to pivot away from you. This virtually ensures that they're going to be trying to trap your right foot, because you're going to be "steering" them away from your left side, making the fabled X with your hands. Right now, you have sort of a ballerina stance, with one leg behind you, somewhat precariously balanced. Bring your right foot back forward and to your partner's ribs and hips, establishing a sort of hybrid knee on stomach position (or go fully into a classic knee on belly if you want, but be sure to block your partner's hips with your right shin as you do this).
The "Yoga Foot" Variation
This next variation is my favorite version of this pass. It assumes a high level of skill from your partner, and if you'd like to see more detailed versions of this pass (and the ensuing scrambles that are inevitable with a good grappler), check out Passing Reverse De La Riva Guard. Once your partner has your right foot hooked with their right leg, it becomes much more dangerous simply to kick backward with a traditional X-pass. Instead, create the same essential frames with your hands (you don't have to flatten your partner out with your head if they're playing RDLR guard, so that actually frees you up for some other options). The main gist here is to make sure that your knee is higher than their shin, and then to swivel your foot (or "Yogafoot") around their shin, keeping pressure on their leg the entire time. Once you get here, again, try to control their hip with your shin, passing to knee on belly.
Favorite butterfly pass
I use the RDLR version of the X-pass virtually every day in jiu jitsu, against white and black belts alike. It is easily one of my favorite ways to get around the guard. Start by getting comfortable with the traditional toreando, then move on to the X-pass, and finish by getting good with the Yogafoot versions. As always, let me know how the pass is working for you, and let me know if I can help you troubleshoot anything else!