In curling, all four players of a team are involved in each of their team’s shots. While the skip, or captain, holds his or her broom for a target and calls the strategy for the shooter, the other two players sweep the stone’s path when deemed necessary.
Sweeping clears the ice of any frost or debris that might slow the stone down or send it off course. Sweeping also polishes the ice, creating a thin layer of moisture that reduces friction and allows the rock to go farther and straighter (up to 15 feet farther with vigorous sweeping).
The “sweepers” are in the best position to judge whether or not the delivered stone has enough momentum to reach its target, while the person in the house can best judge the line and call for sweeping if the stone is curling too much.
Sweeping is allowed between the tee lines, and beyond the far tee line by only one player per team. All four players may sweep at the same time when the stone is between the tee lines. The player in charge of the house may sweep an opponent’s stone once it passes the tee line. Players may also sweep any of their own stones that have been set into motion by the delivered stone.
By the 1990s, the skill of top players had progressed to such a point that, once a team got a small lead, they were simply knocking out one another’s rocks repeatedly, which translated to “boring games” for many spectators. To spice up the game, the World Curling Federation introduced the Free Guard Zone Rule (or Moncton Rule, since it was first tested in competition in Moncton, New Brunswick). Simply put, the Free Guard Zone Rule specifies that players are allowed to bump—but not remove—the first four rocks of a given end if they come to rest between the hog line and the tee line, excluding the house (i.e., the guard zone). Any rock touching the tee line outside the house, or biting (touching) the 12-foot ring at the front of the house, is not considered to be in the Free Guard Zone and may be taken out by the opposing lead player.
When teams take advantage of the Free Guard Zone, there generally are more rocks in play throughout an end, and teams have a much better chance of coming back from a deficit. In turn, strategies have evolved that are significantly different from the old “hit” game, and the sport has become much more interesting for the majority of spectators, as well as for the players.