I could just be kinda dumb, but how exactly do you build off the structures that are further back from the main bridge? Actually, I understnad how to build off them, I just dont' understand how I would link those to my bridge to support it. Anyway, because of this I'm stuck on complex lev 10 or something.
Mind you, you must press "R" to get back into place. Its no good to place a cable to the space between the supports :P
Ok, assuming you're building from a support point behind your bridge.
You pick a material, click that point, hit 'f' to move back (the point should stay highlighted), then click the place you want to link it to.
Hope this helps/makes sense :-)