- 1: Bull block (double rising block)
- 2a: Pull fists away from each other
- 2b: Right back stance left augmented outward block (inner-forearm block), right palm touching left forearm
- 3a: Slowly open the left fist and turn it inward. Slide left foot to shift into left front stance
- 3b: Right horizonal fingertip strike
- 3c: Left hand punch
- 3d: Right hand punch
The opening of Sipjin may be used as a rear bear hug quick escape. Lift both arms to loosen the opponent's grip, pulling their hands apart (step 2a) if necessary. This escape is commonly taught in self-defense sets, although it's usually accompanied with dropping one's weight into riding stance.
|Source: Overland Park Karate|
|Getting a sankyo lock from a rear bear hug. Source: ExpertVillage|
The next movement in the set is the mysterious hand turn. We use this to transition from sankyo to a thumb lock. Doing this allows us to twist the opponent's arm even more as we pull our left fist to our hip for step 3a, causing them to lower their shoulder as you pull back their thumb. To aid this, you also push down their shoulder with the open-handed strike (step 3b)
|Left: Sankyo to thumb lock. Right: Application for the horizontal fingertip thrust|
A variant is to use your left thumb to push in the back of the opponent's wrist instead, rather than hook their thumb, but when practicing with a student we found that the thumb lock allows more control via pain compliance.
Now, wrist locks in a taekwondo form might seem like a stretch to some people. Is there any historical evidence that taekwondoin would put wrist locks into their forms?
|Source: Sihak Henry Cho's 1969 book Self Defense Karate|
Joint locks in early taekwondo are old news. It's hard to realize now, but taekwondo was originally founded as a mixed martial art, incorporated both throwing and locking techniques. Ørjan Nilsen over at Traditional Taekwondo Ramblings has a great post on this called Taekwondo and Joint Locks: A Historical Journey. The core art is still striking. Notice how the point of the lock in Sipjin is to get to the back of the opponent's head, which we then punch.
Although taekwondo's locking and throwing techniques are no longer commonly taught, they were preserved in the forms. Finding the techniques is the way to resurrect these old ideas and increase our understanding of the art.
In other news, The Study of Sam-Il is almost finished. I'm adding a few more drawings.
 Sankyo is the Aikido name for the wrist lock, which literally means "third teaching" since it is the third wrist lock taught in Aikido's curriculum. Since I am unaware of any other name for the wrist lock, I am calling it sankyo.