Creating a Car..Some Panels will not become SOLID FORMS

[BenjiD]

So i am a teacher and helping a student with a personal project. I am simply a beginner at sketchup and am working way above my skill level. I am trying to help him create a car model and right now I am working about 2 or 3 steps ahead of him in order to guide him along the way.

My Issue:

I created a profiles view of the car based upon a tutorial i found on Trimble. That went fine. Now i have begun to create the actual 3D model of the car, but as i am making panels some of them fill in solid with shading, but most are just empty as if they were a wire frame. I have tried to close it into smaller shapes and zoomed in to make sure that the lines are actually connected and there are no gaps, but these are not helping. It seems random to me when the shapes will fill in and when they won't. Is there any way to manually select a shape(by highlight in blue each line) and fill it in with a command? Or some other way to fix this problem?

[TIG]

Posting an image would help us help you...

Any three lines drawn so that they connected at their ends will automatically form a triangular face, because their three shared vertices must always be 'coplanar'.
But if you draw four separate lines that join at their vertices, then their four vertices might not be coplanar, and then no face can form.
This can be resolved by drawings a 'diagonal' line to form two triangular faces from those four edges - because the two sets of three vertices must again be coplanar and thereby support a triangular face.
If you need 'rectangular' faces then use the rectangle tool to draw them - this guarantees that the the face forms. This also works for circles or polygon faces. OR you can draw edges snapping to the same larger face [perhaps within a group] so that the result is a loop that will 'face'.
If a edge needs by a face is erased the face vanishes, it can be remade by redrawing the edge.
If a face is selected and then deleted, then provided that all of its edges remain it can usually be recreated by drawing over one of those edges; some very complex outlines [especially those with inner-loops forming 'holes'] might not 'auto-face' on overdrawing an edge - in that case draw one or more diagonals to split the loop and get two or more faces added, these unwanted diagonal lines can be erased afterwards without compromising the integrity of the remade face.
If you do not draw a full 'loop' of edges then no face will form, since an 'outer_loop' is needed to support any face, no matter how simple or complex its outline is...