The official rulebook of the World Curling Federation is 59 pages long and covers every imaginable infraction, including a stone crumbling to pieces in the middle of a game. (Solution: "If a stone is broken in play, the teams use the 'Spirit of Curling' to decide where the stone(s) should be placed.") However, most of the rules have to do with lines, who can cross them, and when.
A curling sheet has two houses or scoring areas — one on each end — so play can happen in both directions. A thrower begins by placing one foot on the hack, a pair of rubber stoppers sunk into the ice at the far end of the sheet. Grabbing a stone by its handle, the thrower pushes off from the hack and glides forward to the hog line, at which point she must release the stone. Electronic sensors are used in competition to detect faults.
Once the stone is moving, all members of the delivering team are allowed to sweep, although it's usually only done by two team members with the skip directing. Sweeping is limited to the delivering team all the way up to the tee line, a line that bisects the house. Once a stone moves past the tee line, both teams are allowed to sweep it, although sweeping is limited to one person at a time and the delivery team has first shot. Teams can also sweep stones that have been bumped out of position.
Modern curling equipment begins with the stone, a polished circular stone no greater than 36 inches (91 centimeters) in diameter and weighing between 38 and 44 pounds (17 and 20 kilograms). Most competition stones — and all stones in the 2014 Sochi Olympic Games — are quarried from granite on the volcanic Scottish isle of Ailsa Craig known for its strength and water-resistant properties [source: Burns].
Next are the brooms. Back in the day, curlers used corn brooms not unlike the ones in your tool shed. Today, sweepers use two specialized brooms with lightweight carbon fiber handles: a hairbrush broom with short horsehair bristles to sweep away frost and debris; and a bristle-less, flat brush to create the maximum friction to warm the ice. Competition-grade brooms run from under $100 to $200 each [source: Goldline].
The last item of specialized curling equipment is footwear. One shoe has a normal rubber sole, but the other sole can be removed to reveal a slick Teflon surface, called a slider. This is the gliding shoe used when delivering stones. During delivery, pro curlers can glide more than 30 feet (9 meters) from the hack to the hog line.
Now let's trace the history of curling from friendly backyard game to Olympic gold.