Does anyone use this technique and in what ways is it most effective? I imagine it is used as a first blow to stun your opponent before coming in with more hand tecniques, knees, elbows, takedowns, throws or grapples considering the distance. What are it's advantages over a regular hook, if any?

As a side stepping or countering technique. The one advantage that a palm holds is that the hand takes less damage. Also the arm seems to be more relaxed as well, providing the opportunity for more speed and power.

Yes, they are a very good first strike. Like Chen said, they are less likely to do damage to your hand as well.

Check the Jan. 2005 issue of Black Belt magazine for an excellent article on "Combat Slaps" by Jeff Menapace.

I have trained them on the heavy bag, and they are just as strong as a regular hook punch.

i agrre that attak is as strong a s a punch as long ads u train it as much as your punches

this techmique us used in the open hand not so far as to create any more damage or any more painful effect, but used make a transition to a , whats called a jurk hand, or jut sao in wing chun, if blocked, which the practitioner in this art is waiting for, from contact reflexes called chi sao , or sticky hands. he will then make the contact they are looking for. also called asking hand. can also be used as a neck grabbing hand to immobalize ones head pulling it into a punch or crushing elbow. after all, what will hit harder, a semi going 50 mph smashing into a brick wall or a semi colliding with another semi going the same speed?