To shift or not to shift ~ BIU SAO with Sifu Gary Lam 

the biu should arrive before the hook. shorter and deadlier line.

But what if you don't throw the biu sau? You will get hit with the hook and that will be the end of the fight! This is why you MUST FACE THE ATTACK BY ROTATING TOWARDS IT, TAKING AN ANGLED STEP IN to close the distance!