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The free guard zone
One rule separates modern curling from the game before it. It is also the rule most often explained slightly wrong, usually by leaving out the word “indirectly”.
Last updated 2026-08-18
The rule, exactly#
It is rule R6 in the World Curling rulebook, and it is worth reading in full before reading any summary of it, including this one:
A stone that comes to rest between the tee line and the hog line at the playing end, excluding the house, is deemed to be within an area designated as the FGZ. […] If, prior to the delivery of the sixth stone of an end, a delivered stone causes either directly or indirectly, an opposition stone to be moved from the FGZ to an out-of-play position, then the delivered stone is removed from play, and any displaced stones are replaced, by the non-offending team, to their positions prior to the violation.
It protects against removal, not contact. Hitting a guard is
fine. Only knocking it off the sheet is not.
“Indirectly” counts. If your stone hits your own stone which
then removes their guard, you have broken the rule.
It protects opposition stones. You may remove your own guard
whenever you like, which is occasionally useful and always surprising.
Where the zone is#
The zone is the 21 feet of ice between the far hog line and the tee line, with the house punched out of the middle of it. A stone in the twelve-foot ring is not protected however far off the button it sits; a stone an inch outside the rings is.
One extra clause is easy to miss: a stone that was in the zone and gets knocked onto or in front of the hog line while staying in play is still treated as being in the zone. The protection follows the stone rather than the patch of ice.
Five positions people get wrong#
Each of these is a real situation that produces an argument at club level.
Stone six onward: the guard is fair game#
The protection ends the moment the sixth stone of the end is delivered. From then on a guard is an ordinary stone and can be peeled off the sheet like anything else. This is why the first five stones of an end look completely different from the last eleven.
Stone four: knocking a guard out of play#
Illegal. The delivered stone is removed from play and the guard goes back exactly where it was, replaced by the non-offending team. Note what the rule actually protects against: being moved out of play. Red was perfectly entitled to hit the guard — just not to remove it.
Stone four: hitting a guard and leaving it in play#
Perfectly legal, and a real tactic. You may strike a protected stone as hard as you like as long as it stays on the sheet. Pushing a guard back into the house, or shunting it to a place where it protects nothing, are both ordinary early-end shots.
Stone three: removing a guard by accident, via another stone#
Still illegal. The rule says a delivered stone may not cause an opposition guard to leave play either directly or indirectly. Whether you meant it makes no difference at all, and neither does how many stones the collision travelled through on the way.
Stone four: clipping a centre guard sideways#
The loophole. A centre guard is only useful on the centre line, so rather than removing it, teams learned to clip it a few feet sideways where it protects nothing. The stone stayed in play, so the free guard zone rule was satisfied, and the guard was neutralised anyway. The no-tick rule now covers this: the non-offending team may put everything back where it was, or leave it, whichever they prefer.
With scripting off, all five appear one after another. Nothing is hidden.
The tick, and the rule that killed it#
Good rules attract good lawyers, and the free guard zone attracted a very elegant one.
A centre guard is valuable specifically because it sits on the centre line, where it protects the button. Move it four feet sideways and it protects nothing — but it is still, technically, in play, so the free guard zone rule has not been broken. Teams became extremely good at throwing a stone that clipped a centre guard just hard enough to shift it and no harder. The tick shot defeated the rule without breaking it.
Rule R7, the no-tick rule, is the answer:
| Situation | What happens |
|---|---|
| Before the sixth stone of an end, a delivered stone moves an opposition FGZ stone that is touching the centre line off the centre line, or out of the zone | The non-offending team chooses: remove the delivered stone and put everything back, or leave all stones where they came to rest. |
| The same shot puts the stone out of play altogether | The ordinary free guard zone rule R6 applies instead — the shot is simply undone. |
| Wheelchair curling, or mixed doubles | The no-tick rule does not apply at all. |
Note that the choice belongs to the team that was ticked, which is the right design: sometimes a tick leaves a position they are happy with, and a rule that forcibly reset it would hand the offending team a free undo.
World Curling brought it in for international events from the 2022–23 season; Curling Canada adopted it for its own championships from 2023–24, so there was a season in which the same shot was legal in one competition and not in another. The stated reason for the rule was blunt: with tick shots available, the team with the hammer in a tied game was winning at close to nine times in ten, and the sport wanted the outcome to be less predictable.
Why the rule exists#
Because without it, the correct way to play curling is to remove everything.
A team with a lead and the ability to hit accurately could simply peel every stone that appeared, end after end, until the game ran out. It was legitimate, it was effective, and it produced games in which almost nothing happened. The sport knew this and could not fix it without changing something fundamental.
The fix came from a bonspiel. In 1989 an event in Moncton, New Brunswick, looking for a format that would draw a crowd, adopted a practice rule that Russ and Glenn Howard had been using between themselves: the first four stones of an end cannot be removed. It worked immediately. Guards survived, so come-arounds became worth playing, so the game acquired the tactical shape it has now. See strategy for what teams do with it.
Counting to five#
The version of the rule you are playing under depends on where and when, and the count is the thing to get right.
| Version | In force | Protection lasts until |
|---|---|---|
| None | Before 1989 | Everything is removable from the first stone. |
| Moncton rule, four stones | 1989, one bonspiel | The fifth stone is delivered. |
| Three-rock rule | Canadian domestic play until 2002 | The fourth stone is delivered. |
| Four-rock rule | Internationally from 1993–94 | The fifth stone is delivered. |
| Five-rock rule | From 2018–19, current | The sixth stone is delivered. |
| Mixed doubles | Current | The fourth stone of the end is delivered — and it protects every stone in play, not only those in the zone. |
In mixed doubles, until the fourth stone of the end, no stone anywhere on the sheet may be removed from play — including stones in the house and including the pre-placed positioned stones. It is much stronger protection over a much shorter window. See mixed doubles.
Sources#
- Primary The Rules of Curling, R6 (Free Guard Zone) and R7 (No-Tick Shot) World Curling, 2025The wording quoted above, and the mixed doubles variant at R17(e).
- Sport Insight: the rule change that revolutionized curling Sport Information Resource CentreOn the Howards, the 1989 Moncton bonspiel, and the 1993–94 international adoption.
- Curling’s 5-rock rule is having a ripple effect on the game CBC SportsOn what changed tactically when the count went from four to five.
- Primary No-Tick Rule added in 2023-24 Curling Canada, 2023The domestic adoption date, a season behind the international one, and the stated rationale about hammer win rates in tied games.