The bong sao is a defensive helping hand. It serves to change from one side of the opponent to the other, respectively from the inside to the...
encyclopaedie
What we describe as jum sao is the sinking elbow. This minimal move protects the under part of the upper body like belly and liver.
As kwan sao, we describe a move composed of a tan sao and a deep bong sao. It is a defensive as well as an offensive move.