Line-space

The first and most important rule in designing a grid is that it is built upwards from the line-space (typesize + leading = line-space) of the smallest typeface to be used in the design.

They are many advantages to proceeding in the approved manner, of which the greatest is that the method creates logically shaped, sized and graded building blocks which slot together automatically.

One of the corollaries of the method is that no other typeface or typesize can therefore be specified until the smallest typeface is chosen. In practice this means that the designer selects faces, weights and sizes for running text first and for display text afterwards.

This most powerful of concepts in graphic design is also one of the easiest to comprehend and apply. All text and illustrations are locked to the baseline of the smallest line-space, and everything follow from that action.

Jute, André, GRIDS the structure of graphic design, RotoVision, 2006.