Let's say I have this mesh. How would I go about filling the faces? My first instinct was to select these 4 vertices and click Fill Hole. Doesn't do anything. No matter what I select, Fill Hole doesn't do anything at all. In fact, I've never been able to use it a single time in my life. I already know there's a bunch of buttons that don't do anything, like Connect Vertices and Connect Edges. Is Fill Hole also one of those? Why even leave them in? Add them in when they work, that's my advice.