Pin-tumbler and wafer-tumbler locks normally open when the correct key pushes all of the pins or wafers to the shear line. An incorrect key will push the pins or wafers too little or too far. These locks are more difficult to pick than warded locks and are picked by putting tension on the keyhole and pushing the pins or wafers up individually until they reach the shear line. When all of the pins have reached the shear line, the lock will turn as if the key were inserted. Other methods of raising the pins or wafers involve moving an S-shaped pick called a rake through the keyhole to vibrate the pins or wafers to the shear line, or using the pick gun, which bounces the pins to the shear line. It is also possible to pick a pin-tumbler lock with a bump key, which, when struck with a hammer, will bump the pins to the shear line. The force on the hammer should be slightly less than that used for driving a nail, because too much force will break off the head of the key, leaving the rest of the key stuck in the lock. Many newer locks have special pins that make picking more difficult. The special pins are usually spool-shaped and work by wedging into the shear line when pushed up by the pick.