Numbers identify the usual role; the laws govern what the player does.

What this page covers

The primary scope is World Rugby 15-a-side rugby union. Law 3 controls team size, replacements and front-row eligibility; Law 19 controls scrum formation and the phase-specific duties of scrum participants. World Rugby's official positions guide supplies the common 1-15 names, while Regulation 15 supplies the numbering convention for international matches.

Domestic unions, schools, age-grade competitions and modified formats may publish their own squad, replacement and numbering conditions. Sevens, 10s, under-19 scrum variations and Game On are therefore separated below rather than blended into the 15s baseline.

Number, position and legal role are not the same thing

• Shirt number: identifies a player and usually signals the selected position. Within its kit-marking scope, World Rugby Regulation 11.3.8 requires the playing number on the back of the jersey; unions may set conditions below national-representative level.
• Selected position: the role shown on the team sheet, such as fly-half or lock. It is a useful conventional description.
• Legal role in a phase: what the player is doing at that moment—front-row player, scrum-half, lineout thrower, kicker, tackler, ruck participant or non-participant. The law's duties attach to that conduct.

A number 11 may take a pass at first receiver and a number 10 may defend in the back field. Neither move is an offence. By contrast, a player of any number who joins a contested front row without being properly declared and qualified creates a Law 3 safety issue.

The common starting 15

• 1 loose-head prop, 2 hooker, 3 tight-head prop: the front row.
• 4 and 5 locks or second-rows: the second row.
• 6 and 7 flankers, 8 number eight: the back row; all three are forwards.
• 9 scrum-half and 10 fly-half: the half-backs.
• 11 left wing, 12 inside centre, 13 outside centre, 14 right wing: the three-quarter line in the common guide.
• 15 full-back: the usual deepest back-field player.

World Rugby's beginner guide expressly notes regional terminology. Its guide calls 6 and 7 blindside and openside flankers and 12 and 13 inside and outside centres; the international-match regulation instead says left/right flanker and left/right centre. Those labels describe a starting structure, not permanent lanes.

The front row has genuine eligibility restrictions

The loose-head packs to the hooker's left and binds with the left arm inside the opposing tight-head's right arm; the tight-head packs to the hooker's right and binds with the right arm outside the opposing loose-head's left upper arm. The hooker binds between the props and, when that player's team throws in, must strike for the ball under Laws 19.11 and 19.22.

Before the match, Law 3.10 requires each team to tell the appropriate match official which players can play in the front row and the specific position or positions each can cover. Only those players may occupy those positions in a contested scrum, and Law 3.12 makes the team responsible for ensuring they are suitably trained and experienced. A replacement front-row player may start elsewhere, but that does not let an undeclared player become a contested prop later.

The other five forwards complete the scrum

With 15 players on each team, Law 19.5 requires two locks in the second row and three back-row players, completing an eight-player scrum. The locks bind to the props in front and to each other; each remaining scrum player binds on a lock's body with at least one arm under Law 19.7.

The laws do not allocate separate compulsory open-play jobs to shirt 4, 5, 6 or 7. Locks are commonly lineout targets and provide power in scrums, rucks and mauls; flankers commonly cover tackles and breakdowns. The number eight is the hindmost forward in the usual formation and may pick up from the feet of a second-row player to end the scrum under Law 19.36(c). These are phase roles and normal tactics, not a ban on those players passing, kicking or moving wide.

The half-backs organise possession, but can exchange tasks

The number 9 is normally the scrum-half: the player who feeds the scrum and distributes from scrums, rucks and mauls. Law 19.13 lets the scrum-half choose the side from which to throw in, while Laws 19.27-19.32 impose scrum-specific offside positions on both scrum-halves.

The number 10 is normally the fly-half, often receiving the first pass and choosing whether to pass, kick or carry. Another back may become first receiver, the 9 may kick, and the 10 may pass from a ruck. The referee judges the actual action and the applicable offside line, not whether the player performed the task usually associated with the shirt.

Centres, wings and full-back are starting reference points

• 11 and 14 wings: usually begin near the edges and cover finishing, kick chase and back-field work.
• 12 and 13 centres: usually connect the fly-half to the wider backs and defend central or outside channels.
• 15 full-back: usually begins behind the main defensive line to cover kicks and line breaks.

None is legally tied to that channel. Wings may appear around a ruck, a centre may kick, and a full-back may join the attacking line. Their legality is tested by the same open-play, offside, tackle, ruck and foul-play laws as everyone else.

Where a position becomes legally significant

• Contested scrum: Laws 3.10-3.12 restrict the three front-row positions to declared, suitably trained and experienced players. Law 19.5 prescribes the full eight-player formation when both teams have 15.
• Scrum-half: the player acting in that role must obey the Law 19 throw-in and offside requirements; the shirt number does not excuse a breach.
• Lineout: Law 18 refers to “the player throwing in,” not a required shirt number. The hooker commonly throws, but another player may do so and must meet the same position, timing and straight-throw requirements.
• Open play: there is no formation offence because a forward is among the backs or a back is close to the ball. Ordinary phase and offside laws decide legality.

Why the bench is often numbered 16-23

Law 3.4 allows a union to nominate up to eight replacements for an international match; Law 3.5 lets the organiser of another match choose the number, also up to eight. That produces a 23-player match-day squad in many senior competitions. World Rugby Regulation 15 uses 16-23 for international replacements, with forwards before backs, but local competition documents can control the actual team-sheet order.

Do not infer front-row eligibility from a bench number. For a squad of 23, the current Law 3.8 table requires six front-row players in the squad and the ability to replace loose-head prop, tight-head prop and hooker at the first time of asking. Law 3.10's declaration of eligible positions is decisive.

A replacement cannot simply run on

Under Law 3.6, a replacement is made only when the ball is dead and with the referee's permission. If a player joins or rejoins without permission and the referee believes it was done to gain an advantage, Law 3.7 treats it as misconduct and awards a penalty.

If a team has more than 15 players in the playing area, the captain must reduce the number and the sanction is a penalty; the score already standing when the objection is made is not altered (Law 3.3). These are player-number offences in the legal sense. Wearing an unexpected shirt or changing an open-play role is a separate team-sheet or competition-administration question unless it produces another infringement.

A card or injury can change the formation, not the shirt convention

If a team is reduced below 15, Law 19.6 permits its scrum numbers to be reduced as well; the opponent need not match that reduction, and no scrum may have fewer than five players. That means a 14-player side can, in the ordinary 15s law, use seven scrum players while the other side still uses eight.

Front-row safety overrides that flexibility. If a team cannot field a suitably trained front row, Law 3.13 requires uncontested scrums. Law 3.15 says uncontested scrums caused by injury or a yellow or red card must have eight players per side, and Laws 3.17-3.20 may also prevent a replacement or require another player to leave. The detailed sequence depends on squad size and the match organiser's adopted conditions.

Do not carry the 15s map into every union format

• Sevens: the World Rugby 2026 variation replaces Law 3.1 with a maximum of seven players and Law 19.5 with a three-player scrum. The 1-15 map does not apply.
• 10s: the 2026 variation uses no more than ten players and a five-player scrum of two props, a hooker and two locks.
• Under-19 scrum variation: unions may adopt it at defined levels. The front row and locks must be suitably trained; an eight-player scrum uses a 3-4-1 formation, and reductions are matched by the other team down to five.
• Game On and domestic age grades: unions and organisers may reduce numbers, use rolling replacements or adapt scrum conditions within the authorised framework.

Always read the competition appointment: “rugby union” alone does not tell you the team size, replacement process or numbering scheme.

Number 11 acts as scrum-half

Situation: after the starting 9 is replaced, the player wearing 11 feeds the next scrum.

World Rugby 15s, July 2026 ruling: the change of role is not itself illegal. The player acting as scrum-half must make the Law 19.13-19.15 throw correctly and then obey the scrum-half offside duties. The decisive facts are what that player does and where that player stands, not the 11 on the jersey. A competition may separately require the team sheet to record a shirt change or replacement correctly.

A flanker is asked to cover tight-head

Situation: the tight-head is injured. A flanker says they have trained at prop but was not declared before the match as able to play tight-head.

World Rugby 15s, July 2026 ruling: that player cannot enter the tight-head position in a contested scrum. Law 3.10 permits only players declared for that specific front-row position. The referee checks whether another declared tight-head is available; if the team cannot field a suitably trained front row, the scrum becomes uncontested and the other Law 3 consequences are then applied.

A 14-player team forms with seven forwards

Situation: a back has been sent off, both teams can still contest safely, and the reduced team puts seven players into the next scrum.

World Rugby senior 15s, July 2026 ruling: Law 19.6 permits the reduction; the opposition may retain eight, and the scrum must still have at least five. Under an adopted under-19 variation, the answer differs because the other team must reduce its scrum by the same number. The decisive fact is the appointed law variation, not whether the dismissed player was labelled a forward or back.

How to analyse a position or number question

1. Name the format and competition. Standard 15s, sevens, 10s, under-19 and Game On have different team and scrum rules.
2. Separate the shirt from the act. Is the issue only an unfamiliar number or is the player performing a regulated phase role?
3. Count players and check entry. Apply Laws 3.1-3.7 for too many players and replacements.
4. Check front-row declarations. For a contested scrum, confirm the player was declared, position-specific, suitably trained and experienced.
5. Check the formation. Apply Law 19.5 or the appointed variation, including any reduction after a card or injury.
6. Apply the phase duty. Throw-in, binding, offside and lineout requirements follow the actual participant.
7. Check competition administration. Team-sheet and jersey-number irregularities may have a competition remedy even where play itself is lawful.

Claims that are too broad

• “Law 3 assigns every position a number.” No. It controls team numbers and replacements; the position map comes from convention and competition regulation.
• “Six and seven always mean blindside and openside.” That is the common guide, but World Rugby acknowledges regional names and its international regulation uses left/right flanker.
• “The hooker must throw every lineout.” Hookers commonly throw; Law 18 imposes the duty on whichever player throws in.
• “A replacement number proves front-row eligibility.” No. The pre-match, position-specific declaration under Law 3.10 controls contested front-row eligibility.
• “Both teams must always have eight in the scrum.” Not after every reduction under senior 15s Law 19.6; under-19 and uncontested-scrum provisions can produce different requirements.
• “Back row means backs.” No. Flankers and the number eight are forwards.

Governing-body sources and effective version

• World Rugby — Laws of the Game Rugby Union 2026, Laws 3 and 19 and the under-19, sevens, 10s and Game On variations
• World Rugby Passport — live Law 3, “Team”
• World Rugby Passport — live Law 19, “Scrum”
• World Rugby Passport — July 2026 law update and implementation notice
• World Rugby — “Players and positions,” official 1-15 position guide and regional-name note
• World Rugby — current online Regulation 15.1, international-match player numbering
• World Rugby — current online Regulation 11.3.8, playing number on the jersey

Checked on 28 August 2026 against World Rugby's 2026 law book and live digital law assets after the 1 July update. The live Regulation 15 bench wording and Law 3.8 front-row-cover table are not fully aligned, so Law 3 is used for eligibility and no universal 16/17/18 role order is asserted. Unions and competition organisers may supplement the baseline and may set the implementation date for competitions already under way on 1 July 2026.