The double tandem is the form of coupling most used by mushers. The dogs are lined up in pairs, just like at school. Each is attached at two ends to a center line or draft line. The neckline connects, by its collar, the dog to its buddy and to the line of draft. The tugline (tail or back line) is found at the start of the tail, at the bottom of the dog's back. It is fixed to the traction harness.