if you have a plane with servos mounted in each wing in the old days before computers you would use a y harness to link the servos together to function in the same manner as a single servo.but thank god for computers..now you plug the wing servos into different channels on futaba channels 1 and 6 and program the transmitter so when you move your aileron stick both servos will operate travelling in opposite directions for left and right.the travel of each wil likely need ajusting but its a great feature for linking ailerons without harnesses ..I am using wing mixing on my 3D and giant plane..you can add flaperons with it as well ..then you can slow that fast bird to a slow landing somewhere on the club field and not the tall grass.lol..