The ko shako ken was ( like many of our fighting moves) derived from watching the motions of animals in combat. In this instance the tiger. The tiger makes circular motions with his limbs when he strikes. In order to mimmick this(since we don't have the claws of the tiger) you have to bend the top half of each finger to where the point of the finger is now even with it's base or first joint. Keep them tense as to avoid injury.
Point Of Impact:the top or third joint of each finger
PURPOSE:to strike an apponent when he has left a strike from a higher angle unguarded
Strengths:quick, unexpected(usually), good setup for a finishing move
Drawbacks:the force placed on the knuckles is too much for them to handle, this must be used sparingly( too much use will result in injury)