In English mean the side-knees
This trick is used for attack when the opponent loses his balance or to defend the close at tack, by throwing the elbow to throw the knee to the chin or the chest of the opponent.

To protect
Hold the both hands to cover the face and the chest by bending the elbow joint with the tip of the fists pointed to the head (as the plumb lines).

To counter
Twist the body to the left or the right and throw the Elbow to the opponent's rib.