Tackling
Tackling is the only way of legally bringing down your opponent in rugby union.
But there are certain laws on how you can tackle an opponent which you must follow; otherwise you will give away a needless penalty which your team-mates will not appreciate.
When you tackle an opponent, you cannot make contact with their head. This is entirely for safety reasons.
The referee will instantly give a penalty if he sees a high tackle.
And he will also have a few words to say to the tackler if he thinks the challenge was dangerous.
Expect a yellow card and a spell in the sin-bin or worse, a red card and instant dismissal.
So aim for your opponent's chest, waist or legs, you will make a better tackle if you aim for those areas in the first place.
If a tackler and the ball carrier go to ground, the tackler cannot handle the ball because they are not on their feet.
It can be tempting to bring the ball back to your side, but the referee will see it and give a penalty.

Obstruction
In rugby union, you can only tackle a player in possession of the ball.
That means you cannot challenge your opponent at any other time.
So if they do not have the ball, you cannot tackle them. Simple.
Sometimes, a player will deliberately get in the way of an opponent without the ball because they think the attacker has a good chance of scoring a try.
But if the referee sees this, the defender will be in trouble.
A penalty will be awarded to the opposition and the defender could find themselves sitting in the sin-bin for 10 minutes after being shown a yellow card.
Sin-bin
This is a place you should avoid at all costs.
The sin-bin is the bench where all players who have been bad sit out of the game for 10 minutes.
If the referee believes a player has committed a serious foul or shown indiscipline, then he will show them a yellow card, just like in football.
However, unlike football, that player must then immediately leave the pitch.
They then have to sit in the sin-bin for 10 minutes while the game continues without them.
This is music to the opposition's ears because they have one more player on their side.