The Technique of Travel : Page 109
There are various but complicated means of tyingskis to the pack frame, or slipping them through shoulderstraps, thus freeing both hands. Or a line may be tiedto the skis, which are then towed along behind.
Trail breaking.—In soft snow, trail breaking is arduous unless the lead is frequently changed. Choose a suitable length of time, depending upon snow conditions, for each man to lead, and after which he should step aside and take place at the rear. Even if a leader prefers to think that he is an "iron man," he should not overdo his turn at breaking trail. His excess energy may be needed later.