The Iron Wall is a building-block looking like rusty iron with a brick-pattern.
The block can be rotated by pressing and holding R and moving the mouse while holding the left mouse button.
It can be crafted in your Crafting Menu (default key "q") after the crafting-recipe has been unlocked by
- smelting Iron Bars in a Forge from Iron Ore that can be extracted from Iron Nodes on the Stalactite layer or collected from Iron Treasure Chests or Diamond Treasure Chests
- creating Obsidian Rods by putting Obsidian bars into a Processor
- crafting Obsidian Brick Walls
To craft 8 (blocks of) Iron Walls at a time, you'll need (as of R44 in June 2017):
- 2 Melted Wax made of Beeswax in a Forge or looted from Wood Treasure Chests or Stone Treasure Chests
- 2 Iron Bars made in a Forge from Iron Ore
- 1 Obsidian Rod made of an Obsidian bar in a Processor