Bleeds and Safety Margins

Bleeds

If you intend for an image to print all the way to the edge of the paper, it should extend 1/8" beyond the crop line. The extra 1/8" that will be trimmed away is known as the "bleed."

Bleeds are necessary because although modern trimming machines are capable of great precision, they are not perfect.  If you create an image that is precisely the same size as the finished piece, and the press sheet shifts 1/64" while being cut, one side of the image will have 1/64" cut away, and the opposite side will have a white "flashline," 1/64" wide.  By creating auxiliary image area that is intended to be cut away and discarded, you can avoid flashlines. 

Safety Margins

A "safety margin" is often referred to as a "bleed in reverse." If type hugs every crop, and the paper shifts in the cutting machine, some of the type will get cut away. The solution is to keep an 1/8" safety margin between the crop and important design elements - no type or critical image should be located within 1/8" of a crop or fold.