“Die line” is a term used in packaging and brochure design. It basically is a blueprint of the layout of said packaging item, essentially creating a guideline on how the packaging item or the brochure folds or how it should be cut during production.
Often, the dieline is saved as a separate file from the actual design of the package when it is done via computer-aided design software (also known as “CAD” for short), as it is easier to edit it separately. Usually, the die line is not printed onto the package or the brochure itself but rather used as a template based on which it will be folded and further on cut down to size.
Although die lines come in a variety of shapes and sizes, they are all done as a vector, as automated cutting and folding machines require mathematical instructions to operate. Back in the day, die cutting (the process of cutting a rough shape from a piece of material before folding or perforating it) was done manually, and would use very fine die lines as visual guides for the workers to perform precise cuts.
Die lines can be done and then used as a base for further processes on low-strength materials, such as rubber, fiber, foil, cloth, paper, corrugated fiberboard, paperboard, plastics, pressure-sensitive adhesive tapes, foam and sheet metal. In design, die lines are mostly meant to be used on either paper, cardboard, or thin consumer-grade metal (such as the metal used in soda cans).
Die lines can refer to either cutting, perforating or folding a sheet of paper, cardboard or any other material that is being printed on. The arrangement, nature, and shape of the die lines can determine the nature, look and feel of the final product, ranging from shopping bags to rigid or folding boxes.