Fleeting notes are hand-written notes to be discarded after being recast for inclusion in the Zettelkasten as permanent notes (see below). Ahrens assigns the fleeting note to its own category to emphasize its function and to emphasize the habits that he wants users of the Zettelkasten Method to adopt. “Fleeting notes are there for capturing ideas quickly while you are busy doing something else” (Ahrens, 43).

–Zettelkasten.de