They work both on and off lead, with a lot of repetitive...

They work both on and off lead, with a lot of repetitive commands, ... You have to teach them what to look for, and how to distinguish the scent they must follow from the other scents they will come across. You have to do it every day. You learn how to read your dogs signals, because each dog is different, and as you become more familiar with your dog you become more proficient at the process.