This puts you far enough back to see your dog and read his body language. It also allows you when your dog indicates track loss to stop, circle the dog and be standing right on the corner. Another point for those of you who are doing criminal work the 20 feet gives you some distance if your dog tracks right up on a suspect and you need time and distance to react. No matter what line you choose there will be numerous times when your dog comes in close to you and you pull in the slack. Just as you have the line down to 6 to 8 feet the dog hits the track, pulls hard into the harness and the line pulls through your hand causing friction burn.
Some handlers wear gloves while they are tracking.
Personally I don't. I feel that bare hands listen a lot better to the line and what it is saying. As far as the friction burns go I feel that if I get one I deserve one. I should of been paying attention, getting off my butt and going with the dog if he has indicated the track. A number of friction burns can teach a handler a whole lot.