Today, while I practiced with Ernie, I was getting tied up with him with his right hand holding my right wrist, and his left arm across my chest being held by my left hand. I created a split at my right shoulder-kua line to enhance the lock. There was a line from his elbow to his right(rear) foot. My right leg was in front of his left leg with our thighs touching. While holding that line, I moved my right foot back towards his left leg (there was no hitting of the leg though), he fell straight down to the ground as if falling into a hole.
Holding the line was so important while execute a move. We just needed to follow a procedure.
There were definitely cases when it didn't work as well. It was because I moved my top while moving my right leg. Having a clear separation of not moving and moving was the key.