Body thetan (similar to the concept of self) cling to a body because they have lost their free will and is found by locating any sensation of pressure in the body.
In Scientology, the concept of the thetan is similar to the concept of self, or the spirit or soul. According to Hubbard, body thetans cling to a body because they have lost their free will as a result of events in their past. Upon reaching OT III, the individual finds body thetans by locating any sensation of pressure or mass in his or her body. 
