They are attached to the brake leaders on the kite.
When you let go of the handles they apply tension to the brake lines only. This exerts pressure on the trailing edge (back of the kite), causing it
to deflate, removing most of the power/pull of a kite. This, in turn, takes it out of the air.
http://www.youtube.com/watch?v=ZXnl26v-NTEATB
ATB,
Sam
"I never had any friends later on like the ones I had when I was 12 - Jesus, does anyone?" - The Body by Stephen King