7.6 Variations in proportions 

Elements of the same figure must be in proportion to each other unless a difference in proportion is indispensable for the clarity of the figure.

As a preferred alternative to a difference in proportion within one figure for clarity purposes, a supplementary figure may be added giving a larger-scale illustration of the element of the initial figure. In such cases it is recommended that the enlarged element shown in the second figure be surrounded by a finely drawn or "dot-dash" circle in the first figure pinpointing its location without obscuring the figure.