When it comes to rules and regulations, the ruck is one of the more complex parts of rugby .

When a tackled player goes to ground, they must release the ball immediately.

As soon as that happens, the opposition will want to get their hands on the ball, and the team in possession will not want to give it away.

According to the laws, "the ruck is a phase of play where one or more players from each team, who are on their feet, in physical contact, close around the ball on the ground".

So to gain possession, both sides must try to drive over the ball to make it available for their team-mates.

HANDS IN THE RUCK

None of the tackler's team-mates can attempt to handle or pick up the ball once the ruck has formed.

Team-mates of the tackled player can use their hands, but only if they are on their feet.

Referees often blow up for penalties because a player off their feet or from the tackler's team has used a subtle hand to bring it back to their side.

But because of the sheer number of bodies involved in rucks, referees can sometimes miss this particular infringement.

JOINING A RUCK

All players must join the ruck from behind the 'hindmost' foot of the last player.

They must bind with one arm round a team-mate at the very back of the ruck.

Players cannot take shortcuts and join from the sides.

If the referee spots this, a penalty will be given to the non-offending team.

USING THE BOOT

The ball can often get stuck under a pile of bodies, making it difficult for either team to make it available.

Players are allowed to free the ball by using their boot. This term is called 'rucking'.

However, they must ensure they do not make contact with players' heads or tread on bodies intentionally.

Referees are particularly strict on this law for safety reasons, so reckless rucking can mean time in the sin-bin or even a red card.

DIVING IN

All players joining a ruck must be on their feet.

But sometimes players dive in off their feet in an attempt to slow the ball down, allowing defences to re-group.

Referees are particularly strict on this.

BALL NOT FREE

If the ball does not come out of a ruck after about five seconds, the referee will award a scrum to the team he considers to have the greater forward momentum in the ruck.

The line-out is another awesome sight in rugby union.

It is a way of restarting play after the ball has been knocked or kicked out of play past the touch line.

The line-out consists of three to eight players from each side, up to 16 in total, and is taken where the ball went out of play.

The aim of each player is simply to get their hands on the ball for their team.

So how does it work? The advantage is with the team throwing in.

They get the ball because they were not the team who last touched the ball before it went out. They also get to decide how many players will make up the line-out.

FORMING A LINE-OUT

The eight forwards and the scrum-half are the players who make up the line-out.

The most important players are the hooker, the two second rows and scrum-half. They are responsible for getting the ball out to the backs or for the rest of the forwards.

That does not mean the other players have nothing to do. Far from it.

The line-out must be formed past the five-metre line and no more than 15m in from the touchline, and both teams must have a one metre gap between them.

If the referee decides one team has purposely closed the gap, a penalty will be awarded to the other team.

LINE-OUT THROWS

The hooker is usually the player with the job throwing the ball into a line-out. Their aim is to find the "jumpers", usually the two second rowers.

But this is not easy. The other team also want the ball, so they'll be doing all they can to upset the hooker's throw.

The hooker gets a call from one of the jumpers or the scrum half, usually in a code no-one except your team understands, on who to aim the throw at.

They must stand behind the touch line when they make their throw.

And the throw must be deadly straight, otherwise the referee will have the line-out taken again, but this time the opposition get the throw in.

RETAKEN THROWS

The line-out may look very simple, but it has plenty of laws every player must follow:

· The ball must be thrown straight

· All players not in the line-out must be 10m behind the last man in the line

· No player can use a one of the opposition to use as support when they are jumping

· No player is allowed to push, charge or hold another player in the line-out

· No player can be lifted before the ball is thrown

· No jumper can use the outside of their arm to catch or deflect the ball

Depending on how serious the offence is, the referee will either award a penalty or free-kick to the team who did not make the offence.

This is a place you should avoid at all costs.

The sin-bin is the bench where all players who have committed a yellow card offence 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 the yellow card, just like in football.

But unlike in 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.

It leaves their team a man down for a sizeable chunk of the game, giving the opposition the perfect opportunity to push for points

This scrum is one of the best ways of cranking up the pressure on your opponent's defence.

It is given to the attacking side after one of the defending team has grounded the ball inside their own goal area.

But it is only given if a member of the defending team has carried or passed the ball back into their own in-goal area before the ball is touched down.

If this is not the case, the defending team is awarded a 22-metre drop-out.

The other way a five-metre scrum can be awarded is if the attacking team gets within five metres of the try line, but is held up by the opposition's defence.

Because the attacking team has the momentum going forward, the referee will award it the feed at the scrum.

In rugby union, you can only tackle a player in possession of the ball.

Sometimes, a player will deliberately get in the way of an opponent because they think their rival has a good chance of getting to the ball first, but it is not allowed.

You cannot charge or push an opponent when running for the ball, except if the contact is shoulder-to-shoulder.

Blocking an opponent in order to stop them tackling one of your team-mates, or moving in front of a team-mate in order to act as a shield, is also outlawed.

Standing in a position which stops an opponent from playing the ball is also considered to be obstruction.

Players running with the ball after it has left a set-piece cannot make contact with a team-mate in front of them.

And flankers cannot block the opposition's scrum-half as they try to advance around the scrum.

For all these offences, a penalty is awarded to the opposition.

The offender could also find themselves shown a yellow card, which results in a 10-minute spell in the sin-bin.

The eight forwards are the players who form the scrum.

The hooker, two props, two second rows, two flankers and the number eight all bind together in a 3-4-1 formation, ready to lock heads with the opposition.

· The hooker
A key player in the scrum - their job is to hook the ball back towards the waiting scrum-half .

· Two props
They make the hooker's life easier. They bind on tightly on both sides of the hooker, leaving no gaps between them, and try to drive the opposition back.

The prop to the left of the hooker is called the loose-head because they have one arm free when they bind.

The prop to the right is called the tight-head because they slot in between the hooker and the opposition loose-head.

· Two second row forwards
They bind tightly together and pack down behind the front row, putting their heads in the gaps between the hooker and the props.

· Two flankers
Bind on to both the props and second rows on either side of the scrum.

· Number 8
They pack down behind the second row forwards, putting their head between the two second rows.

Rugby is one of the few ball games where the ball cannot be passed forwards.

That means a player moving towards the opposition's dead ball line must pass the ball to a team-mate either along or behind an imaginary line running at right angles to the side of the pitch.

The same principle applies even when players are not passing the ball.

If they fail to catch or pick up the ball cleanly and it travels forward off a hand or arm and hits the ground or another player, it is called a knock-on.

The same applies if a player is tackled and the ball goes forward.

If a player fumbles the ball but catches it before it has hit the ground or another player, it is not a knock-on.

When a knock-on occurs, the referee will stop play and award a scrum to the team which has not knocked on.

If the ball is thrown forward at a line-out, a scrum is awarded 15 metres in from the touchline.

If the referee decides a player has intentionally knocked on or thrown the ball forward, a penalty is awarded to the other team.

And if the referee decides the other team would have scored a try if the intentional knock-on had not taken place, a penalty try is awarded.

The one exception to the knock-on rule is the charge-down.

If a player charges down the ball as an opponent kicks it, it is not a knock-on, even if the ball travels forward.

Rugby union is played by two teams of 15 players.

Although the aim of the game is simple, there are many laws which make can make it hard for the new viewer to keep track of what is going on.

AIM OF THE GAME

The aim of the game is very simple - use the ball to score more points than the other team.

You can run with the ball, kick it and pass it, but passing forwards is not allowed.

Rugby is a contact sport, so you can tackle an opponent in order to get the ball, as long as you stay within the rules.

There is a referee, aided by two touch judges (one on each side of the pitch), to decide how the rules should be applied during a game.

There are several ways to score points.

• A try - five points are awarded for touching the ball down in your opponent's goal area.
• A conversion - two points are added for a successful kick through the goalposts after a try
• A goal kick - three points are awarded for a penalty kick or drop goal through the posts

If both teams score the same amount of points, or no points are scored, then the match is a draw. In some cases, extra time is played to decide who wins.

DURATION

A game of rugby union has two periods of 40 minutes each. In international matches the referee will stop the clock for stoppages.

Between the two halves, there is a maximum 10-minute interval, after which both teams change ends.

KICK-OFF

Before the start of the match, the referee tosses a coin to decide which team will kick off the match.

The captain of the team that wins the toss gets to decide which end he wants to attack first, or whether his side or the opposition will kick off.

The game is started by a place kick or a drop kick from the middle of the halfway line.

The ball must travel forwards at least 10 metres from the kick-off. If it does not, the opposition get the choice of a scrum or line-out on the halfway line, with the advantage of the feed or throw.

If a penalty or drop goal is scored during the game, play is restarted with a drop kick from the halfway line. The team that has conceded the points takes the kick.