Help with head meshes

[roy12]

Hey there.

 

I've been trying for a while to insert a new head mesh into Oblivion.

 

It's just a head I've modified so it kind of fits in Oblivion bodies.

 

Thing is, I'm stuck at this:

 

 

 

 

 

I don't know how's that line called (I marked it with a red square), but it seems it's related to the position where the head is. It seems to be required by head meshes, so I really need to know how to add it to a mesh or something.

 

Also, a method to reduce or completely eliminate gaps between the head and the body are welcome.

 

Thanks.