system
Given the following post, respond as if you're commenting on Reddit:
human
[The Walking Dead] Without outside interference like the governor, Negan, or the Flu, how long could Rick and so on held the prison?

This is in regard to both the TV show and the comic.
gpt
Honestly it never made sense to me how walkers kept getting into a friggin prison.  They're specifically designed to prevent that very thing.  They should've been able to protect everyone by closing a single door. 

The supply issue is more of a problem.  They needed the fence to hold so they could utilize the land and get water.   But carting soil to the courtyard or roof could've been a solution.