They are almost always the six forwards in the side. The scrum is formed at the place where the infringement occurred. However, all scrums must take place at least 10m from the touch or goal lines.

Background Rugby Union scrums which collapse possess a higher injury risk than completed scrums. A mechanically stable scrum should limit the motions which generate uncontrolled and hazardous ...

Additional scrum analysis showed that only 5% of all scrums collapsed, but the propensity for injury was four times higher (2.9 (1.5 to 5.4) injuries/1000 events) and the severity was six times ...