How it works.. You get like three 4x4x4 grids where you can build anything you want and place any traps you want too. When you are finished building you save that design (ex. port-a-fort-1). You can then craft it whenever as long as you have all of the materials you used to make it. These custom port-a-forts carry over so you can use them whenever you want. Just to prevent any funny business if you change the design for port-a-fort-1 then any of those port-a-forts you have crafted are either recycled or lost. Also, to prevent it from actually giving you too much of an advantage, you can use upgraded structures but it still takes the same amount of time for them to reach full health.
I don’t know, a couple things I was thinking that would be cool port-a-fort ideas.. trap tunnels, cool designs like llamas or logos, and defensive forts that would actually be useful in save the world.
Source: https://www.reddit.com/r/FORTnITE/comments/t7njjf/cool_idea_i_had_custom_craftable_portaforts/
