You beat me to it! :) Was just gonne make a Q about it.
I can't place them at a edge of a foundation and strech it down to another foundation, since then, the upper foundation is in the way...
You haft to place a "Convayer Pole" on the edge first, then you can make it go down.
By the way... I LOVE THEM! they make it much easier to organize the factories :)