copy and paste

So this is is one of the questions I always had problems with, but never got around to actually post it. When making a symetrical map you need to copy half of the map. The first time it's very easy, because theres no logic on the map most of the time, but after that it always gets tricky for me...

i have a small kayak rack i am building, and whenever i paste special to copy it (it contains ropes, so i can't use normal paste) it inverts the roof into a V shape and reverses the brackets so they face towards the center post instead of facing away. Normal paste dose not do this. I am telling...