Iron Scaffolds are the sturdier version of Wooden Scaffolds. They still need to be supported by other scaffolds below, but they're able to extend 5 blocks out from the blocks that support them. They are easy to set up / demolish and even act as ladders for reaching the building height easily. As of version 1.90, they currently cannot be sprayed with Construction Foam.
Rightclick: Places one Scaffold (as normal) Leftclick: Places one Scaffold on top of the scaffold you clicked on. This only works if you have already placed one Scaffold.
Reinforcing Iron Scaffolds
You may reinforce your Iron Scaffolds by using an additional Iron Fence. Right-clicking on an existing scaffold with an Iron Fence will reinforce it. This will consume 1 iron fence. The scaffold being reinforced must also be part of a pillar of scaffolds connected to the ground. Once a scaffold has been reinforced, you may then place additional scaffolds adjacent to it, over air blocks, up to 12 blocks away. Note that this type of scaffold (due to it being made out of iron) needs to be broken by a pickaxe to retrieve it. You will also get the iron fence back from reinforced scaffolding. Thus, no materials are wasted when reinforcing a scaffold.