There are two methods to bump dents: off-dolly and on-dolly. The hammer-off-dolly is used to raise low spots and lower high spots simultaneously. The hammer-on-dolly is a method used to apply a concentrated force on a small area. Place the dolly against the top of the damaged spot. The hammer blow exerts a pinching force on the metal, and a small amount of metal is crushed and flattened between the hammer and the dolly. Each blow should overlap the last and no two blows should be on top of each other. A correct hit will create a high-pitched "ping" noise, while a miss will give you a dull or dead sound.