Place holders are terms used to refer to objects or concepts that are used to fill in a space or represent something else. In the context of this crossword, MAPS (4 letters), TABS (4 letters), and ATLASES (7 letters) are all place holders. MAPS are two-dimensional representations of an area, usually showing physical features such as roads, rivers, and mountains. Tabs are small pieces of material that are used to hold documents together or to mark a page in a book. Atlases are collections of MAPS, usually bound together in a book form.