Figures 93 and 94 are examples of two methods of showing an article on a drawing. The former is the orthographic method which shows three views projected upon three planes of reference as used in descriptive geometry, and the latter is the isometric method, used particularly in free-hand sketches and now used on finished drawings.

In many cases, two orthographic views will show fully the details of an article, particularly if one is a cross-section view. Simple articles may be shown by one view. In Fig. 94 the isometric axes AB, AC and AD are 120° apart, that is, the angles Cad, Dab and Cab are 120°, with AB vertical.