This is a flapper style door for the purge chute. It allows for poops to fall out and then drops back down to help seal in unpleasant odors / particles depending on what filament is being used. It uses a piece of filament as the hinge and a 3M command style strip to affix. It also fits nicely while using the Elegoo mini-carbon poop catcher included on the USB drive and at least one other chute style catcher (https://makerworld.com/en/models/1061314-purge-guide-for-the-elegoo-centauri-carbon).
In accordance to the maker of a similar X1C door, this is not a typical remix but an allowed modification being posted with his direct permission (https://makerworld.com/en/models/186239-poop-chute-door-for-p1s-x1c#profileId-511675).
The author remixed this model.
Resized to work on the Elegoo Centauri Carbon