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I'm still a beginner and decided to model a lightsaber from a CG GEEK tutorial linked here.
I've been having some trouble joining two faces after running into trouble from double vertices in my mesh. I noticed it when I applied a subdivision surface and I've been having trouble solving it. The biggest detail that I've noticed is that the new vertices that were created when I tried to fill in the gap with the fill tool, aren't recognized as a face by Blender. Thank you for your advice.