I teach the hammerfist
Thats a strike with the bottom part of your hand. Make a fist, use the bottom section near your little finger. Make the action you would if using a hammer.
Great news you can do the same motion with an open hand.
You can do this move from many angles downwards, upwards, left or right and even on an angle. Very short motion, rapid action. I use this alot in mma (mixed martial arts) and self defence.
but lets give you the edge. Same motion add weapon and the best weapon are the one that are handy, ready available and often we have on us all the time.
Poke a pen or keys out the bottom use the same hammerfist action, Your mobile phone, magazine or water can be used the same way.
so can knifes, screwdrivers, a stick, a book, brick, a torch and a credit card, even a apple.
Make safety your priority
Be your own body guard