Many chefs use a large knife to make pitting olives easy. Place the flat side of the knife on top of the olives and tap the knife with your fist to split the olives and slip out the pits.
I prefer to use a meat mallet. Give the olives a good tap with the mallet to crack them. Slip the pits out of the cracked olives.
Don’t have a meat mallet? Take a can—whatever you find in your cupboard that fits easily in your hand and has a little weight behind it. Carefully clean the lid, and then lightly crush the olives with the can and slip out the pits.