Crouch, touch, set. Collapse.
"Any idea what has gone on there, Geoff?"
"Not a clue, George, it's the dark arts, innit?"
Over the next seven weeks, tens of thousands of people in packed stadiums and millions watching on television will scratch their heads as 16 men become embroiled in a battle of strength and will. They will engage and re-set as the scrum takes centre stage.
Irish fans will finger their rosary beads for the safe passage of Mike Ross. They may not know exactly why the health of this giant, 33-year-old Corkman is so important to the team, but they are scarred by Twickenham and the crushing memory of what happened when he got injured last year.
Ahead of the Six Nations, we asked him to demystify the dark arts of the front-row.
Ruaidhri O'Connor: Can you put into layman's terms the difference between a loosehead and a tighthead, and explain why the latter is so important?
Reggie Corrigan: The two positions are completely different in the way you carry them out. I often compare it to writing with your left and right hands, they're that different.
The most important thing in the scrum is that the loosehead prop (No 1) is against one other player and the tighthead prop (No 3) is against two.
Because of the way a scrum is formed, with the right shoulder of the loosehead being against the right shoulder of the tighthead, it means that the opposition's hooker (No 2) is also pushing against the tighthead.
That alone makes it a really arduous task, because he has two players pushing against him as opposed to one. The other thing that makes it difficult is, because of the imbalanced way that the scrum is set up, three against three, the two hookers tend to be the fulcrum.
Imagine a merry-go-round, it is like that. The scrum will naturally spin on the axis of the hooker. The tighthead is trying to stop that spin, the loosehead is causing that spin.
In the engagement, the loosehead prop is, naturally, in underneath the chest of the tighthead. When he goes forward, usually he drives up.
As well as trying to create forward force, the tighthead also has to create downward pressure and 'lock the scrum down'. If he doesn't do that, when the force comes against him, it will force him up into the air and you often see the scrum pop up and have to be re-set.
The tighthead's job is so difficult because, not only does he have two people driving against him, he also has them underneath him on both sides because the hooker is doing the same thing. Even though they are not supposed to, they drive him up into the air.
The way it works out, it is always an upward force so he must pin those two guys down as well as going forwards and steadying the scrum. There is huge force.
The tighthead also leads the hit, they are the first point of impact. The force has been measured as between 1.5 and two tonnes.
During the 'crouch, touch, set', you have a split-second to have all of your set-up right. A split second to get into a good, solid and comfortable position that you can hold for a period in the scrum.
Loosehead is an easier position, that's the bottom line. I played both and it is 10 times easier. I played (a bit of) international rugby at tighthead and I dreaded it. It is just so difficult.
RO'C: Why do scrums collapse?
RC: There are an awful lot of factors. If, on the engagement, you get bumped, jostled, twisted or turned and can't get into the right spot – you're in trouble.
Sometimes, when props get into that difficulty they deliberately collapse it, because they don't want to get into trouble, which is fair enough because if you are in that position you can get screwed by your opponent.
On other occasions, a hooker can pull them or a second-row may not be with them or a wing-forward drives them in at a wrong angle and it collapses. You have to consider that a prop is connected to a hooker, a second-row, and a flanker. There is a unit of four working and the same on the other side.
People often wonder why it is so difficult and so technical. There are so many different components that have to be on the money 100pc to get it to go right.
So, if any of those other three attachments to the prop are not synced, if they are not going in together, if they pull him the wrong way or drive him down... the second-row might drive the back of the leg into the ground for example.
Add to that, there is another meat-head on the other side trying to do the exact opposite and destroy you. It makes it very difficult.
Sometimes, there is too much of a gap between the front-rows. There is supposed to be a metre gap. When a prop goes to engage, his legs are only so long. He sets up with his feet square and launches himself off both feet into contact and gets to full extension point.
As you go forward, if you don't bring your feet up underneath yourself, then you end up with a fully extended body. If your legs are straight, you will collapse because your balance is gone.
Also, on the engagement, you see props going in with their heads and their shoulders below their hips. So, when they make contact, they go straight down. If they do that too much, there is no way the opposite prop can hold him.
RO'C: Many penalties will be given for props having "slipped their bind". What does that mean?
RC: The reason that there is a bind at all is to create stability. The loosehead will be pushing his arm upwards and the tighthead pushing his down. This is often confused with deliberately collapsing the scrum, but this process is necessary in order to create the stability of the scrum.
The tighthead has to have something to push against. The reason that the loosehead binds up and out is because he is supposed to apply upward pressure to allow the tighthead to push down against. Otherwise he has nothing to push against and it collapses.
RO'C: What is the referee's role in all of this, and do they have a good enough understanding?
RC: All scrum coaches want their props to be like a coiled spring so when he calls 'set' and they engage, they use the power of the legs. Because of their legs being coiled, when the referee delays the call it makes it hard.
The referees' understanding is not good enough. I have done a few referees' seminars and the refs are dying for the information.
They have touched on it, but not enough. For an area of the game which is so debated, they should do more on it, there should be more clinics.
Props try and get away with stuff – most of the time you're coming in at an angle to gain an advantage for your team.
Some referees are not quite strong enough at dealing with that in games. Sometimes the decisions they make are more about laying down a marker as a warning or to stamp things out because they don't want it going on all game, not because they know what is wrong, and you see some terrible decisions.
RO'C: Ireland go into the Six Nations in a precarious position because of the reliance on Mike Ross. How can this be addressed?
RC: The only solution to the current prop shortage is an adequate level of qualified coaching at all under-age levels.
New Zealand didn't have a great number of props coming through; they realised this and they developed 'the front-row factory'.
In France, they have tried to make propping sexy again and encourage young players into the position.
The French have a great academy for developing young props, but it wasn't always so. They had a major problem with foreign props coming into their system a few years back but they put resources into it and funded development projects. The French forwards coach Didier Retiere was instrumental in this development.
They ensured it was properly funded and a clear strategic plan was put in place – they even have a machine that simulates the scrum that was made by a man who develops aircraft simulators, that couldn't have been cheap to build. It simulates all the movements and tests the props in controlled but real situations, just like a normal scrum.
In the old days, the criteria for being a prop was that they were big and sometimes a bit overweight. Nowadays, they need to find big back-rows, and No 8s in particular, at school and see if their body-shape might be better suited to the front-row.
If players like this were taken and trained from an early age and shown the nuances of the position, then by the time they reach the under-age representative levels they would be in a good position to push for provincial squads. That is what they do in France and that is what has to be done here.
You cannot talk to a guy at 24 and hope he can turn into a prop.
We're not spreading the net wide enough, we're not putting scrum coaches in the provinces at under-age level and giving them proper support and backing and giving it a protocol on what they have to do.
The IRFU did advertise for a national academy scrum coach almost 12 months ago after the senior team were embarrassed in the scrum in Twickenham but unfortunately as of yet no one has been appointed to the role.
If that was done, it would take a long time, but eventually you would see the fruits of that.