Team roping is the only pro rodeo event where two athletes share one run, one clock, and one paycheck. The header rides out first on the left side of the chute, throws first, catches the steer around the horns (or around horns-and-neck, or just the neck, those are the three legal catches). Then the header dallies his rope to the saddle horn, turns the steer so the steer's back end faces the heeler.
The heeler has been riding parallel on the right. As soon as the steer is turned and the back legs are in reach, the heeler throws. Clean catches both back legs, that's called "two feet." One leg is a five-second penalty that usually kills the time.
Once both ropers have a solid dally, they face each other. The timer stops the instant both horses are facing each other with ropes tight. Times at a pro rodeo typically fall between 4 and 10 seconds. A 3.8 is a blazing run.
The barrier, a rope across the front of the header's box, keeps the header from leaving before the steer does. If the barrier breaks early, it's a 10-second penalty. Veteran headers time the barrier within a tenth of a second.