I always thought it was called a "Dual Tow". You have two cables of different lengths. The deal was that the more experienced would, more often than not, be on the longer rope and fly in the low tow position. The other would fly in the normal, high tow position. On the ground run you treated the wingtip as the tug and only once the tug was well airborne did you assume your correct lateral position. We used to move the club gliders (K18's & K13's) from Dunstable to Shobdon for our annual wave expedition using this method. The tug? typically a 150 Super Cub but we also used a Chippy. In hindsight probably marginal but it beat driving.
PM