A folding knife, typically a pocketknife.
An organizer that papers are kept in, usually with an index tab, to be stored as a single unit in a filing cabinet.
A virtual container in a computer's file system, in which files and other folders may be stored. The files and subfolders in a folder are usually related.
A machine or person that folds things.
Something that wraps around or surrounds something, as a sheath encases its blade.