Grid Design Basics - The Graphic Design: Reference and Specification - page 58

c o m p o s i t e g r i d s
Composite grids primarily define structural
thresholds and alignment points and can
be applied to an existing typographic unit
grid to give a designer additional indica-
tion of where to place content within a
sequential document. A composite grid
may indicate the placement of columns,
page headers, folios, notes etc.

The benefit of adding a composite grid to
the typographic unit grid is that it includes
primary flow lines and can make laying
out pages easier. The combination of a
composite grid with a typographic unit grid
easily accommodates both text and other
visual elements.

This example shows what the typographic unit grid on the
opposite page would look like with flow lines (or thresholds)
added.

In these examples, it is possible to see what the combined
typographic unit and composite grid would look like with
content added.