Skull fractures are commonly divided into fractures of the vault or the base of the skull. For the former, they are either linear or depressed. Linear fractures occur when the head is thrown against a wall or sustains deceleration injury. The force is usually considerable. Depressed fractures occur when objects fall onto head. Although they look horrible, depressed fractures are actually less dangerous than linear fractures, for the momentum of the falling objects is much smaller than the momentum of the whole body.