Gracie Barra Bristol, (BJJ), Can Sönmez, Bristol, UK - 05/01/2012
Last time, I went through what I see as the basics of half guard, which is essentially creating a frame to block their cross-face, get an underhook, then get onto your side. Somewhat reluctantly, I also went through the lockdown, which I was in two minds about teaching as it so often becomes a stalling position (not to mention it locks you in place, so it isn't something I generally advise people use).
This time, I began with a brief discussion of maintaining top half guard, which I wanted to use to illustrate a typical mistake in knee shield, which is my personal favourite way of holding half guard. Basically, I was just sharing what I tend to do, if people let me get away with it by keeping their knee shield too low. I immediately move to tightly underhook their arm then brace my other elbow against the back of their head, dropping my hips and sprawling back. From there, I try to gradually put them flat on their back, then establish the usual cross-face and gable grip.
Note that a good cross face involves you gripping under their head, so that your bicep is pressed into the side of their neck. Your shoulder drives across their throat and may also shove against their shin. The idea is to not only make them uncomfortable, but also prevent them from turning towards you (which they generally need to in order to escape).
I don't like hurting my training partners unnecessarily, as I've discussed before, so this is about the borderline for me in terms of 'dirty techniques'. It's possible to be quite mean with a cross-face, so use your own judgement based on the people you are training with (i.e., I wouldn't recommend smashing your shoulder into the throat of a small white belt who is trying out their first class. However in a competition, it may be entirely appropriate).
Getting on to the knee shield itself, (also known as z-guard, and I think Geeza calls it shin guard, though that may be slightly different), the central idea here is blocking their hip with your leg, meaning they have more difficulty moving forwards. One option is to position the knee across their hip, which means you can keep your feet locked.
However, that also means you knee is quite low, so there is the disadvantage that they may be able to shove your knee to the mat and pass, like we did earlier. To stop that, you could put your knee up high into their chest, like Caio Terra. As ever, there are pros and cons, as putting your knee up high may open up a gap between your feet.
If you leave a gap between your feet, it is possible your partner may then be able to simply circle their lower leg around and free themselves. So, if you can't cross your feet, then clamp them together, to create a barrier to that leg-circling. Alternatively, clamp them onto your partner's leg, again to make sure there isn't a gap.
The hand positioning is relatively similar to the Indrek Reiland version of half-guard I showed last time. Caio Terra gives a few more details on the 'paw' grip, noting that you should be blocking their arm with your wrist rather than your hand, as that makes it harder for them to bend your block backwards. The other arm forms a frame against their neck, meaning that the elbow of that arm is close to the knee of your knee shield (this comes in handy later for transitions and techniques, which I'll probably get into next week).
Terra also mentions that he likes to go in close with his head. The reason for that is to make it harder for them to circle their arm around his blocking 'paw'. If they can get past that, they can attack for the underhook. It's possible to keep re-establishing the paw, but then you'll probably get into an extended battle of who can swim their arm faster. Hence why Terra prefers to cut out that space by curling inwards.