Depressed fractures are known as "fractures a la signature" (signature fractures), as their pattern often resembles the weapon or agent which caused it. These fractures are caused by local deformation of the skull. In this, fractured bone is driven inwards into the skull cavity. Gutter fractures are formed when pa of the thickness of the bone is removed so to form a gutter, e.g., in oblique bullet wounds. Ring or foramen fractures are fractures which encircle the skull in such a manner that the anterior third is separated at its junction with the middle and posterior third. Diastatic or sutural fractures in which separation of the sutures occur only in young persons, due to blow on head with blunt weapon. Ref: Textbook of Forensic Medicine and Toxicology by K S Narayan Reddy, 27th edition, Page 216-217.