When building the scrum, it is important that both players and coaches understand the role and importance of the key sub units within the scrum. The left hand triangle comprises the loose head prop the hooker and the left hand lock in Attack the role of the loose head prop is to ensure that the hooker is in a stable and effective position to be able to strike for the ball in defense their role is to pressurize the opposition tight head the right-hand triangle comprises the tight head prop the right hand lock and the flanker on the right hand side of the scrum in Attack the role of the right hand triangle is to Anchor the scrum and to counter the opposition attempts to wheel or turn the scrum in defense then role is to apply pressure to the opposition loose head prop and hooker.