Connecting through an empty line

Today, I was teaching the class, as part of Fist Under Elbow, to grab with a tightened fist, and then do in-with-elbow without moving the fist or powering on the fist more. After that, we moved on to finding the line for in-with-elbow against the opponent's chest. If the opponent's chest is a horizontal straight line across, we needed to identify a T, in which we needed to perform in-with-elbow along the line perpendicular to the opponent's chest. After that, I demonstrated we could replace the perpendicular line with an empty line if we can pull precisely at the bottom of the T.  The intersecting point and the power (pulling) point are connected through some body parts of between the opponent and me, but the structure through those body parts allowed the empty line to be maintained, as illustrated as the dotted line in Figure 1.
Figure 1