The Defender's Wiki - Back walls

Back walls are usually less advanced versions of front walls - without water, snipers' nest and thinner. On some maps you may need to make the back wall 3 blocks thick to prevent boating into the woolroom from backpit, then you can also add water to it, but usually back walls are 1-2 blocks thick. We build backwalls primarily so the rushers can't just straight up run into the woolroom after they get past the main wall and 1 block is enough for that, however I tend to build back walls 2 blocks thick sometimes

#Where/how to build a back wall -

• Usually, maps have two bedrock walls on the woolroom path. The back wall should be built on top of the first one (screenshot below), unless there's only one bedrock wall then you shouldn't build a back wall, just a front wall
• You can mine the blocks on top of the bedrock wall, if there are any, but you can do that later as well, so it's not that important
• You should build the back wall until you hit the build limit, unlike front walls where you need to leave space for the snipers' nest

#Types of back walls -

Back walls are not too different from front walls and there isn't really many types of them, but I'll showcase some, in case you're a beginner
All walls in this section follow the best practices (if possible).