Bone smashing, also called bone smashing theory or bonesmashing, is a controversial theory predicated on the principle of Wolf's law (the idea that bones will grow in response to stress placed on them) which asserts that you can cause bone growth by exposing the bone to repeated blunt trauma. This is usually used to cause growth of the facial bones, such as the cheekbones or mandible.
The practice involves hitting with an hard object precise parts of the face such as chin and cheekbones for the purpose of fixing a recessed chin or getting prominent cheeksbones.