I needed to replace my toilet’s tank to toilet gasket, and in the process disconnected the toilet’s supply line. The rubber “screw like” object shown above fell out when I did this.
After finishing the gasket replacement, I forgot to put this back, and everything worked fine with no apparent leaks. But now I want to put it back, but I’m not sure what it does or what orientation it previously had. After researching and watching videos of flush valve and supply line replacements, it appears nobody else has a part like this in their toilets. I’m honestly beginning to think this object wasn’t supposed to be where it was.
Here’s an image of the disconnected supply line:
Here’s an image of the flush valve from inside the tank. Brand name: fluidmaster, probably installed ~2011.