1. Loosehead prop & 3. Tighthead prop
The role of both the loose- and tighthead props is to support the hooker in the scrum and to provide effective, dynamic support for the jumpers in the line-out. Along with the second row, the props provide the main power in the push forward in the scrum. For this reason they are usualy the strongest and heaviest players in the team. Under modern rules non-specialists are not allowed to play as props (or hooker) as specialist skills are required to ensure the scrum does not collapse, a situation which can be very dangerous sometimes resulting in crushing or breaking of the neck and spine. If there are not enough props or hookers on either team (and no replacements are available), uncontested scrums will be set.
A tighthead prop is so called because they pack down on the right-hand side of the scrum and so (because the players engage to the left of their opponents) their head fits between the opposing loosehead prop and hooker. In contrast, the loosehead prop packs down on the left-hand side where their head is outside that of the opposing tighthead prop. Although it may look to the neutral observer that the two positions are quite similar (and some players have the ability to play on both sides of the scrum), the technical challenges of each are quite different. Jason Leonard (England and Lions) and Gethin Jenkins (Wales and Lions) are rare in being able to prop on either side at the top level.
The laws of the game require the tighthead prop to bind with his right arm outside the left upper arm of his opposing loosehead prop and similarly they restrict what the loosehead prop can do with his left arm. Although the scrum half may put the ball in on either side of the scrum, he is unlikely to choose the tighthead side because otherwise the opposing hooker would be between him or her and his or her own hooker. Hence, the laws implicitly require the loosehead prop to be on the left side of the scrum.
Props are also in the position of being able to direct the movement of the scrum in moving side to side to prevent the other team's scrum from "wheeling" the set scrum and forcing another "put in" from the opposing side.
Outside of the scrum and line-outs Props use their great strength and weight to win rucks and mauls for their teams and to make large drives forwards with the ball.
Props in the International Rugby Hall of Fame include: Jason Leonard (England and Lions), Syd Millar (Ireland and Lions) and Wilson Whineray (New Zealand). Whineray is also a member of the IRB Hall of Fame.
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