See [[Tree testing (information architecture)|tree testing]].
In a ''reverse card sort'' or card-based classification, an existing structure of categories and sub-categories is tested. Users are given tasks and are asked to complete them navigating a collection of cards. Each card contains the names of subcategories related to a category, and the user should find the card most relevant to the given task starting from the main card with the top-level categories. This ensures that the structure is evaluated in isolation, nullifying the effects of navigational aids, visual design, and other factors.
Reverse card sorting is ''evaluative''; it's used to judge whether a predetermined hierarchy provides a good way to find information.
