Dirt Wall

Can be placed like any other backing wall. Map-generated dirt walls do not stop enemies from spawning and are not be suitable for a dwelling. NPCs can live in houses made with a placed dirt wall background, which will prevent enemy spawns. Note that placed dirt walls aren't "compatible" with world generated dirt walls; they will not merge with each other, as the game treats them as different kinds of background.

Generated dirt walls will not drop anything when destroyed.