A Metal Wall was a craftable, placeable item made out of Low Quality Metal. They could only be placed on a Metal Foundation between two Metal Pillars. They appeared as a standard wall made out of rusty sheet metal.
Metal Walls could only be destroyed by placing 4 Explosive Charges on them. They did not decay, and could not be destroyed by hitting them with a Pick Axe, Hatchet, etc. When placing Explosive Charges on a Metal Wall, players had to take into account any previous damage done to the wall (it was impossible to repair them).
They could only be rotated by scrolling the mouse wheel before being placed. It was impossible to rotate a wall after it had been placed.
There was once a bug with doors that allowed players to glitch through them. This was eventually fixed.