What are the rules of the tackle in rugby?

• A tackle: "the ball-carrier is held and brought to ground by one or more opponents".
• Brought to ground: lying, sitting or with at least one knee on the ground.
• Height: tacklers must tackle below the sanction line, which is the shoulder line in elite rugby and lower in community rugby.
• The tackler must: "Immediately release the ball and the ball-carrier", move away or get up, and be on their feet before playing the ball.
• The tackled player must: make the ball available immediately "by releasing, passing or pushing the ball in any direction except forward", and move away from it.
• Not lie on it: the tackled player must not lie on, over or near the ball to stop opponents getting it.
• Others must: stay on their feet, and arrive "from the direction of their own try line" before playing the ball.
• On the ground: a player on the ground may not play the ball or tackle.
• Offside lines: created when at least one player is on their feet over the ball.
• The tackle ends: when a ruck forms, when a player on their feet takes the ball away or when the ball leaves the area.
• The sanction: a penalty for each of these.
• Unplayable: if it is not clear who offended, a scrum to the team last moving forward.

The glossary has the tackle, the breakdown, the jackler, the high tackle, the offside line and the penalty.

Rugby lets play continue after a tackle, where other football codes stop. That only works if the ball comes free quickly and fairly, so the law gives every player a job the moment the carrier hits the ground. With fifteen a side, support usually arrives within a second or two, so the contest for the ball is quick and crowded.