This article is from the Rugby Union FAQ, by roelofs@f2s.com (Mees Roelofs) with numerous contributions by others.
A team is made up out of 15 players, who all have fixed, different tasks.
By definition, the teams will therefore play the same formation, with only
some slight variations in use. Rugby therefore is different to for instance
soccer with its endless number of 'playing systems' (4-3-3, 3-5-2 etc.) or
cricket, where a player may be moved to a completely different position on
the field (ie from silly point to gully).
A player's tasks are made clear by the number he wears, as this indicates
his position (unless he's a substitute or has switched position during the
match). This means a player does not get a personal number for his entire
career, as you tend to see in most American sports. The IRB has laid down a
numbering scheme for international matches, which is commonly adopted by
other teams as well.
1 Loosehead prop
2 Hooker
3 Tighthead prop
4 Left lock (or second row)
5 Right lock (or second row)
6 Blindside flanker (or breakaway, or wing forward)
7 Openside flanker (or breakaway, or wing forward)
8 Number eight (or breakaway, or lock)
9 Scrum half (or halfback)
10 Fly half (or standoff, or outside half, or 1st 5/8th)
11 Left wing
12 Inside centre (or 2nd 5/8th or left centre)
13 Outside centre (or centre or right centre)
14 Right wing
15 Full back
The players numbered 1 - 8 are called forwards or the pack. They normally
form the scrum, even though this is by no means mandatory. The props and
hooker are called the front row. With the locks they form the tight (or
front) five. The numbers 6 - 8 are called the back row, loose forwards or
loosies. The numbers 9 - 15, those usually not in the scrum, are called the
backs. Numbers 9 and 10 are often referred to as halfbacks, while 11, 13,
and 14 are called three-quarters. In some nations the number 12 is
considered part of them.
As can be seen there is a lot of variation in the names of the positions.
Apparently, the IRB has standardized the names, yet the alternative names
are still as common as ever before. A problem with standardized names is
that the positions themselves are not as standard as they seem at first
sight. For example, there is a slight difference between left and right
centre on the one hand and inside and outside centre on the other hand. One
may play wingers on the open side and the blind side rather than left and
right and you may come across left and right flankers.
Common variations in the numbering are the interchange of 6 and 7
(particularly in South Africa and Argentina) and of 11 and 14. However,
many numbering oddities, such as Bristol and Leicester wearing letters
instead of numbers and Bath not fielding a #13, now belong to the past as a
result of all sorts of standardization directives issued.
There also are regional variations to the way line-ups are listed. Most of
the time, the first player mentioned is actually the number 15. The two
mainstream styles of listing a line-up are 15-9 then 1-8 and 15-1. However,
you may see the centres messed up and the same is often being done to the
back row. In the end, knowledge of the players is required in order to
understand the line-up.
 
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