Board Thread:New Features/@comment-1526346-20160620043426/@comment-27073024-20160620051853

is used to further organize the categorization of pages. It does not categorize a page. The sortkey parameter is required for the magic word to work, and should be placed directly above the category links of an article.

"is a magic word used to modify the sequence of pages shown on category pages. The given sort key in a specific page is used to determine that page's position in all category pages where the page is listed. Note: The specific page will still be listed with its original title, regardless of the modified sort order. The sort key can be overridden for specific categories, if their tags contain a differing individual sort key."

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As FishTank mentioned, how - specifically - is it not working for you?