Mud Wall

Mud Walls are naturally-occurring background walls found in the Jungle and occasionally Underground Jungle. They can be destroyed with a Hammer, but cannot be picked up nor crafted. Therefore, they can never be placed or utilized in any other way by the player.

If Mud Walls are sprayed with Dark Blue Solution they will turn into "natural" Mushroom Walls that likewise don't drop anything when destroyed. If these Mushroom Walls are sprayed with Green Solution they will revert back into Mud Walls or natural Jungle Walls, this seemingly being determined by layer level.