This is one of my favorite passes. It plays off of the double under stacking pass for when I cant get my hands connected (which is most of the time at the black belt level).
Hand placement on the belt is very important. Make sure to watch the video and reference where my grips are and how I tuck my elbows.
You will find the more that you do this pass the more your body angle plays an important roll in not only getting around the corner, but also avoiding having your thigh caught by your opp