Quote - I'm not really sure what you mean by 'thick'
If you mean solid ,then just attatch another face at the open end.
If its a more complex shape then you'll have to put up a screenshot

Hope that helps

Actually, Iv'e solved the problem.  Threre really is no thick 3D objects.  For example a 3d box has 6 thin sides.  It appears to have thickness (to an observer) but really does not.  In other words, the inside of the box is filled with air.