Folders are a commonplace metaphor in computing environments, constituting a link to physical work materials and are a key means for individuals to impose order on their digital work materials. This paper presents the findings of a novel qualitative study examining folder use by 12 information workers, using logging to accurately capture how folders were used in individual everyday work over 6 weeks, and challenging participants to work without using folders. Through observation and interviews, the study provides new descriptions of how folders are used and the dependence some study participants had on their folders to think and create, as well as to access files. The findings call into question whether search and recency-based lists of files could fulfil the functional role of folders, identified as key means for individuals to construct and specialize their work environments. Implications are discussed for document management tools, and more generally for operating system design.