the other aspect is the transition from striking to grabbing/grappling/wrapping up, etc....since you need an open hand to transition to these things - may as well hit with some type of open hand. or like mentioned, if hitting with a forearm - why close the fist?

Well, one thing is that the surface area of a knife hand is smaller and narrower than say, an elbow or a palm heel. This means it is easier to slip a knifehand under someone's chin or through a block than it would be to use an elbow or palm heel. Of course, the angles of attack are different too so it can't be used in all situations.

...I was addressing the point made earlier that some things are stereotyped or interpreted to be 'knife hand', when in fact they aren't used as such (for instance, as hedkikr pointed out -a 'shuto' is not a 'knife hand', it's a circular movement used for simultaneous parry and striking the neck with the edge of the hand at an angle and often carried thru as a wrapup).

however, I've been hit in the neck before with fingertips...it friggin hurts. the kind of pain that you feel in your toes.

every strike doesn't have to necessarily be a show stopper (although I agree, it's the goal in spirit) - but something like striking with fingers...if it's there and you're in a precarious position...maybe it happens to be the best thing to do at the time. but spend any length of time training it? nah. I haven't done the hand condition. I wouldn't underestimate it though if someone trained it and knew what they were doing.

Techniques like gohon or nihon or ippon nukite are very effective towards eyes, throath/side of the neck, plexus.
You can condition the fingers so you can strike as hard as with fist but this takes a lot of conditioning.
I condition only through a pincher and finger tip push-up, so I limit myself to the targets I stated above. I also hit a gymnastics matras put against the wall with gohon nukite sometimes.

In sparring I use it in a randori (free technical fighting, setting up free combinations in a continous fighting rhytm, usually at 50 - 75 % speed and power). In jyu kumite it is usually a fight stopper to the eyes or throath, but then I do not use it too much (too much competition fighting I guess).

In sanchin,tensho and sesan kata, there is a movement where the fingers are thrusted into the flesh and then fists are created after the thrust into a hikite movement. You can interprete that as grasping skin/flesh and then twisting it.
When training it with partner, this hurts but in sparring/clinching you can take a lot more and it gives nice bruses. Sometimes it has effect in free fighting but I don't know in a real altracation. It is effective though with skin from the side of the neck, pinching also the artories or the throath pinching the adams apple or the cheeck (but caution, counter attack = biting, make sure you grab the skin and move upwards) or the testicles.

Ther are also fingertip strikes like in sepai towards the testicles (after the elbow lock, relaesing and 180/270 turn)
or like in hakucho (Matayoshi) towards the eyes.

In theory, those spearhands in Sanchin don't have to be impact weapons. Really, you're striking near the ribs, and those ribs are stronger than your middle finger. In other versions of the same kata, you're doing crane-style grabs. I just can't see striking someone's belly, getting hold of the ribs, and turning them over. I know we might be OTS at this point, but how is this movement different from Seiuchin? It's a difference of angle.

In my version of Seisan, the closest thing to a spearhand is three ridgehands after the first turn.

If you want to rely on conditioning, you can make anything do anything. I'm talking about practical application for someone who hits a makiwara a few times a week but does not bother with the whole hot sand thing, since he has to write and type for a living.

I'm not trying to dis. I just want to know how the spearhand can be useful. Even for eyegouging, a three-finger strike is better than a one-finger strike.

in relation to the nukite, or spear hand again it is misrepresented in alot of more 'modern' systems, ie in kata it is practised as four fingers together, thumb on side.

I was shown, and have researched it to be inaccurate, a slight change that makes alot of difference to the structure of the strike-

Simply allow your index and little finger to almost meet, over the other 2 fingers, and allow the palm to cup a little, compresing the bones of the hand, the thumb folds down to meet the middle knuckle of the index finger.

You are now hitting with a much more effective hand, imagine conditioning the hand significantly and you should see that the strike has utility.

As a starting point one of the bunkai I teach in Pinan Sho, for the nukite with the other hand under the arm, think of pulling a head down and striking the nukite into the side of the neck.

Nearly all of the open hand, and come to think of it closed fist methods seem to have been changed for ease of learning and easy training,

I think this is mainly down to lack of use of the open hand methods which I feel were significant in the older art, when of course general training was perhaps for a different reason in the main.

I try my best to make this right at our dojo, but I am at best a part time enthusiast!

the hanging sand bag is the way to go for all the single knuckle and open hand techniques, its a safe training method that had good effect,

I posted a picture of my hanging sad bag on my Blog recently.

Its also perfect for toe kicks!

Im midway into writing a paper discussing the open hand and single knuckle methods, ie proper hand formations, once its done I will link it up so people can see and hopefully get something from it.

I like the sonnal chigi (knife hand strike). It slips in to places other strikes won't sometimes and has it's uses. I see it as something to be used like a half fist or leopards paw strike. I wouldn't use it all the time but at certain times, it is the perfect strike or block for that matter.

I like it as a block because after you make contact, it is a simple matter to close the hand on the limb and turn it into a grab all in one motion as opposed to making the fist, hard blocking, and then trying to grab. They slide into the back of joints well too.

They work well for me but may not work for you or fit into your style of fighting. It works for me.

Scottie

I was thaught to to bring the middle finger on top of the index and the ring finger, pushing the 3 fingers together, creating a striking point of 3 fingers. By 'cupping' the hand a little, the 3 fingers will be aproximantly the same length and fingers are bend in a way that if the resistance of the targetted area is to hight your fingers will bend in a natural way. The thumb and little finger press on each side to support more tension in the hand/fingers, thumb is bend.

I once read about a makiwara for finger strikes, made out of a boards that can be hold by one hand and tapped with the other. A,other instrument is called a TOU, wich is a bundle of small bamboo sticks that you hit with your fingers and try to penetrate as deeply as possible. (never used it though)