Today I built my first set of doubles in the yard at work. It wasn't all that hard either got it together pretty good. It's no big deal you hook the dolly up to the pin-tel hook on the first trailer then you hook up the chains and then do all the air lines and electrical and all that good stuff. Raise the landing gear on the rear trailer and of course make sure the dolly is all hooked in and the safety latch is around the lock jaws and hooked in. It wasn't all that hard went back pretty easy.