The Double Knifehand Outward Block (also called sonnal momtang magki) is an Augmented Outside Block that's performed with knifehands. Most often this block is performed in a Back Stance, but it may be performed forward-facing stances as well, such as the Tiger Stance.
For this explanation assume the block is being done in a leftward direction.
- The right Knifehand (the augmenting arm) is chambered palm-down straight out to the side of the body, or with the elbow bent slightly upward.
- The left Knifehand (the blocking arm) is chambered palm-up at the right side of the waist.
For both arms, imagine keeping the elbow in the same location in space, rotating only the forearms.
- First, the blocking arm begins to travel up toward the shoulder. The other arm does not yet begin to move.
- Only when the blocking arm has reached the shoulder, does the forearm of the right Knifehand begin to arc so that the right knifehand ends with the wrist in front of the solar plexus, knifehand is palm-up.
- Meanwhile forearm of the left continues its arc upward like a Knifehand Block so that it ends directly in front of the shoulder, palm facing somewhat away from the body, as if to block an incoming strike using the outer-forearm.
Of course the above directions are reversed for a rightward block.
When performed in a Back Stance (where it's most commonly seen) the two forearms wind-up more-or-less pointing in the same direction (i.e., pointing to the side of the body). When performed in a Cat Stance however (for example, in Taegeuk Pal Jang) the blocking arm is pointed forward away from the body, while the assisting arm is held in front of the body; in other words, in this case the two forearms are more-or-less perpendicular.