The experimenting is over for curling's five-rock rule. From the clubs to the world championships, curlers are adapting to the newest wrinkle in the sport this season.
Rocks in front of the rings can't be removed from play until five rocks have been thrown in an end. Previously, the rule was four rocks in what's known as the free guard zone.
So the team with hammer now has the option of throwing a second guard that can't immediately be removed on the next shot.
Sounds simple, but there are a host of ripple effects from new strategies to more demands on shotmaking skills, particularly at the second position.
"It's another thing to kind of wrap your head around," Olympic gold medallist and television commentator Joan McCusker said.
The world's top teams have been playing the five-rock rule in the World Curling Tour's Grand Slams for the last four years.
The World Curling Federation's vote to adopt the five-rock "FGZ" for 2018-19 put it into widespread use this season.
The theory behind the change is there will be more rocks in play, fewer blank ends, the ability to come back from a big deficit and thus fewer blowouts in which teams shake hands early.
Elite teams such as Jennifer Jones, Rachel Homan, Brad Gushue, Kevin Koe and Brad Jacobs got a head start on it playing in Slams.
Those who have played few or no Grand Slams, as well as club teams, are still on a learning curve.
"If you look at the very top at Jennifer Jones, Rachel Homan, Brad Gushue, Kevin Koe, those kind of teams, for sure I think they're going to have that advantage," Edmonton skip Kelsey Rocque said.
"They've played in the Slams consistently ever since the five-rock rule (was) introduced really. Definitely I think they'll have that slight advantage for the first maybe year before everybody else catches on."
Darcy Robertson's Winnipeg team played five-rock in one Grand Slam prior to this season. So she and her teammates are still adjusting to it.
"Even for us six weeks later we are more comfortable, although we still do have a lot of questions in our heads," Robertson said.
"Sometimes a situation comes up we haven't seen before. We're still learning."
Down 6-1 after four ends, Rocque lost in an extra end in a game in Calgary earlier this month. She says her team's comeback was an example of the five-rock rule at work.
McCusker said her mixed team gave up six in the second end at Regina's Callie Club one night.
"We came back and it was tied up coming home," she said. "Did we employ the five-rock rule? Oh, you betcha. We're throwing everything out there and not taking anything out."
Two-time world champion Russ Howard invented the free guard zone rule in the 1980s to jazz up curling.
The WCF implemented the four-rock rule in 1993. Canada went with a three-rock version before adopting four in 2002.
Howard, now a television commentator, believes only the top teams can really maximize the five-rock rule because of difficult get-out-of-trouble shots required.
"I think it's a good idea, but the best way for me to describe it is it's only applicable to the (top) one or two per cent in the world in my opinion," he said.
"Unless you've got a skill set to start making runbacks and double-peels, then you're going to be stolen on. At the club level, I think you'd be out of your mind to throw two corner guards."
Now that the team without hammer can't peel a guard with the second's first stone, seconds need more finesse shots in their arsenal.
"I wouldn't even say 50 per cent of my rocks are hits. I would say 75 per cent are softer-weight shots," said Shannon Birchard, who plays second for Kerri Einarson.
"It's only when we're up a certain amount that I'm clearing."
But skips wrestle with how big of a lead do you need now before playing defence.
"I think the key with the five-rock rule is knowing when to switch gears," said Einarson's third Val Sweeting.
The five-rock rule is changing the game again, but precision shotmaking will always be paramount, according to McCusker.
"You can have great strategy with five-rock, but if your team makes no shots, you still lose," she said.
The WCF has revamped world ranking criteria, making results from Olympic and Paralympic Games points equitable with world championship points. Games points were previously double the weight.
Points will also be scored over four years instead of six, so only one Winter Games is taken into consideration.
The first set of rankings under the new criteria has Canada ranked first in the world in both mixed doubles and mixed team curling. Canada's Michael Anderson won the world mixed team title Sunday in Kelowna, B.C.
Canada ranks second in men's and women's team curling behind Sweden and fourth in wheelchair curling behind China, Norway and Russia.
— Gregory Strong contributed to this story