The lethal Reverse Dela Worm guard. There are few guards that put your opponent in such a powerless position. With the back exposed and facing you at an unfavorable angle, your opponent is now between a rock and a hard place.
The choice is to either do nothing and have your back taken or post with the near arm and get armbared.
Even if your opponent opts for the more dishonorable option – laying on their back to take the sweep, you can still get on top, right into mount. From there you can maintain the RDLW grip and yank your opponent on top of you to take their back.
TL:DR Learn this well and your opponent is screwed.
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