The second hand pattern of the Wing Chun system is called Chum Kiu which means “searching for the bridge”. The bridge refers to the bridge connecting you and an opponent.
Once you have a contact, the hand sensitivity and chi sau training can kick in to find the centreline and attack down it very quickly. But before you can do this you must “bridge” the gap between you an your opponent. Of course an attack straight down centreline can also be a bridge too – and you can “bridge” with a punch, or a kick as well as a contact/blocking movement.