In plain language
There must be at least two ways to find pages (menu + search, sitemap, index...).
Who it affects
People with cognitive or visual disabilities who prefer search, sitemaps, or alternate nav styles.
How to check
Confirm at least two working routes to reach content (navigation, search, sitemap) and spot-check they actually find deep pages. Worked example — A nonprofit's donation form: open the sitemap link: if it's empty, outdated, or missing whole sections of the site, it fails as a genuine second way.
Common misconception
Having a navigation menu is not “two ways.” This rule requires two genuinely independent routes, like navigation plus a working search, not two variations of the same menu. Real example: on a ride-hailing app's trip booking screen, the only way to find a specific ride option is to scroll through the booking flow screen by screen — there's no search, site map, or table of contents offering a second route to it.