Overview
Ippon Ken literally means "one point fist", but to my knowledge, there's no specific martial arts term for the first knuckle. It's a reasonable precision weapon for striking vital points, although I prefer the middle knuckle, which feels stronger.
Used in these katas
Hangetsu
Striking targets
Any pressure points including temples, eyes, solar plexus, throat, neck, between the ribs, biceps, inside of thighs, top of foot
Technique
Make a tight fist, then extend the first knuckle. Firmly press the thumb against the edge of the curled finger to re-inforce the strike and prevent sideways movement.
Strengths
Good for precision striking.
Weaknesses
Can only be used against soft targets. Danger of breaking the finger - don't extend knuckle too far!
