The palm strike. It's the heel of the palm you make contact with, but it's referred to as a palm strike. To execute a palm strike, its important to have the right hand position. The hand is pulled back as far as possible, locking the wrist and the fingers should be allowed to curl slightly forward. The palm and finger tips should face the target.
Contact is made with the very bottom of the palm just before the wrist.
When knuckles meet skull during a confrontation, the skull will always win. I don't think anyone will argue that former heavyweight Champ Mike Tyson is an accomplished puncher. When Mr. Tyson punched former Heavyweight contender Mitch Green on the head, Tyson's hand broke. Neither man wore gloves for the bout. The fight took place on a Harlem street corner.