What is kite running in The Kite Runner?

Kite flying was a major pasttime during the winter months in Afghanistan. Major tournaments were held in all of the big cities, and Kabul's annual event was the largest in the country. In the sport  described in Khaled Hosseini's The Kite Runner, it took two people to fly, fight, cut and run the kite. Amir and Hassan used to make their own kites from scratch, but they soon discovered that purchasing ready-made kites gave them greater success against the other boys. In competition,

The rules were simple: No rules. Fly your kite. Cut the opponents. Good luck.

In the Afghani version of kite flying, the lines of string were coated with ground glass and glue. After they dried, the lines were wound around wooden spools and attached to the kites.

... every boy in Kabul bore telltale horizontal gashes on his fingers from a whole winter of fighting kites. I remember how my classmates and I used to huddle, compare our battle scars on the first day of school. The cuts stung and didn't heal for a couple of weeks...

When fighting other kites, the object was to strategically position the kite so that it could forcefully attack and cut the opponent's string. The kite runner then retrieved the defeated kite whose string had been cut.

The real fun began when the kite was cut. That was where the kite runners came in, those kids who chased the windblown kite drifting through the neighborhoods until it came spiraling down...

Hassan was Amir's kite runner--and

... by far the greatest kite runner I'd ever seen. It was downright eerie the way he always got to the spot the kite would land before the kite did... 

Besides running and capturing the defeated kites, the kite runner also held the spool for the kite flyer during the fight. The winner of the tournaments was always the last kite flying, and the most "coveted prize" was the last kite to fall.