The outside two panels must be the largest, and each successive panel beginning with the 3rd must be about 1/16” smaller than the previous panel to fold properly.
This works well for brochures that have a lot of information that can be segmented on each panel, or one big image that can spread across the fully opened brochure. For example, a tourist brochure with activities described on each panel and the fully-opened inside is a map of the area.
See also: single fold, tri-fold, gate fold, zig-zag fold, accordion fold, french fold, map fold