Artemis BJJ (MyGym/Bristol Sports Centre), Can Sönmez, Bristol, UK - 18/02/2015
For this fundamental attack from the guard, you first need to isolate their arm. Easiest way to do that is to grab their wrist with your same side hand, then also grab their elbow. Pull their arm across and pin it to your chest. You're then going to put your same side foot on their hip, clamping the knee of that leg to their shoulder (essentially you're trying to take away their space, as well as blocking them from easily pulling their arm backwards).
If they're wearing a gi, grab their opposite collar with your wrist-hand (keeping hold of their arm with your elbow-hand) and pull them down. If it's nogi, grab their head. Next, kick your other leg into their armpit, aiming to further break their posture and get your leg across their back. You're also going to use that to swivel your own body and get a better angle. From here, you can then push their head out of the way with your head/collar grip and bring your hip-pushing leg over their head. Squeeze your knees, lift your hips and pull down gradually on the wrist for the tap.
A common problem is that your partner will 'stack' you up onto your shoulders, making it difficult (though not impossible) to finish the technique. This is a common problem with the triangle too. To prevent that situation, push with your legs, as well as really knocking your partner's posture when you kick across with the armpit leg. You can also 'walk' back on your shoulders to recover a more extended position if they are squashing you. Finally, angling the leg you have by their head can help (like on Adam Adshead's old DVD), as that makes it tougher for them to push into you.
Teaching Notes: The one extra bit I added was that it's possible to roll them through into mount once you're in a good armbar position, by grabbing and lifting their knee while extending your legs. I might also emphasise where you're establishing the fulcrum for the armbar: a common problem was that people didn't have the elbow far enough through in order to hyperextend it, ending up just bending the forearm instead. I didn't end up going through Sahid's handy drills this time round, but I'll include them here for next time:
To help with teaching this, my training partner Sahid has a useful sequence. It starts with drilling the leg positioning. In closed guard, your partner is going to put their elbow on the opposite side of your belt knot/belly button. Bring your leg on the same side as that arm up, so you can pin your knee against their shoulder. Your other leg kicks up into their armpit. Use that to turn your own body, also bringing their body down with the armpit leg. You can now bring your first leg over their head, keeping your heels pointing down (don't cross your legs).
Next, you're going to add in one of your arms. They aren't generally going to give you their arm, so you'll have to drag it across yourself. Reach across with your opposite side arm and grab slightly above their elbow. Still keeping your ankles crossed, lift your hips, then as you drop them, pull the arm across your body. You want to end up with their arm between your forearm and bicep, enabling you to clamp your elbow to your side while also pinning their arm. Your hand goes to your chest.
Step your knee up on their trapped-arm side, again pressing it into their shoulder. Make sure you don't raise that knee before you've pinned the arm, as opening your guard at that point may give them enough space to start escaping. Then finish as before, kicking your other leg up into their armpit, swivelling, bringing your first leg over their head and completing the submissions.
The third and final stage adds in a collar grip with your free hand (if they have a collar: if not, grab their head). Reach for their collar/head after you've pinned their arm, then pull them down. You can also use the elbow of that collar gripping arm to block the elbow of their trapped arm. That prevents them from trying to bring the elbow of their trapped arm to your other side hip, as that would scupper your armbar attempt.