In the world of prepress, we use bleed margins for bleed area only. All marks (folds, perfs, etc.) are indicated in the slug area. This area is also used to place in the file information pertinent to the print vendor, i.e., stock, ink, folding and other finishing instructions, etc. This area might also include special instructions to anyone picking up the file for future use. We have found it to be an invaluable tool.