see also PaperPrototype
LowFidelityPrototypes are paper mock-ups of GUI screens. We draw them on standard 8 1/2 X 11 pages and use post-it notes to represent dialog boxes and pull-down menus. This often gives users a very good feel for what screens will look like and how they will interact with each other, without giving them the false impression of "completeness" that a screen-based prototype gives. -- KyleBrown
A great way to walk through use cases. Arrange the paper mockups on a wall (or on a white board), then "walk through" them to simulate a user experience. -- DaveSmith
CrcCards provide a low-fidelity prototype of objects. An Apple HyperCard User-Interface Guidelines document had suggested prototyping stacks with index cards. I already had a WikiWikiHyperCard stack for recording designs (see BezelMenu). From this it was only a small step to paper. -- WardCunningham