Applying optical methods to a simple inspection problem, such as the presence or absence of an assembly component, is likely the least restrictive of any machine vision application. The setup, alignment, and components can be made very simply by using any feature which appears different if the component of interest is present. Gaging to verify proper construction, however, can be a much more complicated task. To take advantage of the capability of machine vision and other optical technologies, some flexibility in part position, orientation, and speed of presentation may be desired. This paper will review the types of methods available from optical methods for industrial dimensional metrology. The emphasis of the discussion will be 2D and 3D gaging applications.