[Question] Getting rid of holes in a custom model

[sharda]

I want to post some model edits so I can get rid of my leecher tag but I'm having a problem. I'm making a custom chainsword model but when I load it in wow modelviewer it is missing some of its faces but in milkshape these faces are intact, albeit solid black. Does anyone know how to fix this?
I have pics of the faces in question in modelviewer and in milkshape but I can't link them cause I haven't made three posts yet, PM me if you need them.

Edit: Nevermind, I figured it out. For anyone that has this same problem: In milkshape, select the faces that show up black and got to face > Reverse vertex order (ctrl+shift+f also works). This will turn the faces inside out and they will now show up properly on your model.