In martial arts, a knifehand strike is a strike using the part of the hand opposite the thumb , familiar to many people as a karate chop . Suitable targets for the knifehand strike include the carotid sinus at the base of the neck , mastoid muscles of the neck, the jugular, the throat, the collar bones, ribs, sides of the head, temple, jaw, the third vertebra , the upper arm, the wrist , the elbow , and the knee cap . In many Japanese, Korean, and Chinese styles, the knifehand is used to block as well as to strike.