Andrew Smith is a 3rd-degree BJJ black belt based out of Richmond, VA (Revolution BJJ). He runs BJJ Path, a video tutorial website.
The Hip Switch
The hip-switch half guard pass is a huge cornerstone of my jiu-jitsu game, and I think most black belts would say the same thing. On the one hand, if you have the underhook and the crossface when you're on top in half guard, life is good. On the other hand, everyone knows this. This makes it impractical to rely on getting a dominant half guard position whenever you're on top. Enter the "hip-switch" technique, so named because of the complete positional change that your hips go through. We'll take a look at the basic mechanics of the position, some key details that make the difference between passing a high-level practitioner's guard or not, and a second entry into the position.
Note: it is perhaps obvious at a glance that this position closely resembles the half guard Kimura pass series I use. Rest assured that the Kimura passing game is best started with a solid understanding of the hip-switch technique described herein, so it's well worth taking the time to get good at it. As your partner dives their left underhook under your right arm, start repositioning your body so that it's perpendicular with your partner's body (as opposed to very nearly parallel, which is what your partner wants). This means that your left elbow needs to be below your partner's shoulder, but somewhat above their elbow, very much akin to a Kimura set up. Once your partner is flat, "switch" your hips so that they are facing your partner's hips. Next up, walk your trapped foot up so that your shin is propped straight up, at 90 degrees to the floor. This will facilitate free your leg.
Meanwhile, use your left hand to grip either your partner's pants or belt, freeing up your right hand. Use your right hand to push their knee down, but be careful not to open your elbow too much (or else your partner will hook your arm with their hand). One way to do this carefully is to use your forearm to slide their knees down while planting your hand on their hip (another way is to simply straighten your arm and be careful). If your leg comes free, just backstep and finish the pass. If not, it's time to slide your hips back in order to create space for your left shin to wedge in there. Push with your hand and pull your leg up in the air to free it, and finish with a backstep into a reverse kesa gatame position.
Here are a few key details that will make this pass work at a higher percentage, and against far better training partners. First, pummel your left arm around your partner's inevitable crossface-blocking hands (in a perfect world, you can flatten them out and pass their half guard if you can get the crossface, but again, everyone knows this now). After you swim in between their hands, change that angle so that you are essentially cross-body on your partner, but be sure to flatten your partner out by driving forward. Note: your left elbow should be pinching in tight just above your partner's left elbow, and your belly button should approximately touch their belly button (don't go too far forward!). To facilitate the "hip-switch" maneuver, bring your left knee in to touch your right knee, and then allow your right foot to "walk" (first on your toe, and then on your heel) until your right shin is pointing straight up in the air. The biggest thing from here is simply not to rush; take your time, and you are almost definitely going to pass your partner's guard. Note: it's possible that your partner knows How to Counter the Hip Switch from Half Guard, so patience really pays off, especially if they're gripping your pants leg.
This last entry into the hip-switch position is a great way to get into the position (assuming this is a strong way to pass the guard for you) and can be much easier to reach than doing this from half guard.
Remember that everyone knows the game these days. Starting up with your partner sitting up and with you standing, stab your lead leg in between their legs, and just switch your hips on the way down. You can drive your partner flat with your hip and then slide right into the position.
This position is near and dear to my heart, largely because I used it successfully in competition to win some of my favorite matches, and also because I've derived a Kimura system largely around this guard pass. Jiu-jitsu moves can be like that: one day, you find something that just clicks, and changes everything, and your entire game can start to revolve around whatever the new thing is. Don't be afraid of not being well-rounded if this happens to you, because your motivation to get into the position you want is going to encourage you to get out of bad spots and navigate through tough terrain, thus forcing you to work on everything anyway. As always, let me know how these techniques are working for you!