Box Construction
Objects of rectangular shape may be more easily drawn by
means of box construction, which consists simply in imagining
the object to be enclosed in a rectangular box whose sides
coincide with the main faces of the object. For example, in fig
below, the object shown in two views is imagined to be
enclosed in a construction box.
This box is then drawn lightly with construction lines, I, the
irregular features are then constructed, II, and finally, III, the
required lines are made heavy.
Figure 5.21 isometric box constructions