What is the process to add crop marks to a design?

Adding crop marks to a design is essential for printing, as it guides the printer on where to cut the final piece. The method of selecting an object and creating trim marks is the standard process in Adobe Illustrator to achieve this. When you select the object you want to add crop marks to, using the appropriate feature allows you to generate trim marks that signify the exact dimensions and cut lines for the final printed material.

The other choices do not accomplish the goal of adding crop marks. For instance, the crop tool is primarily used for cropping images rather than adding crop marks. The paintbrush tool is designed for drawing and painting within the design, and does not generate any cut or trim information. Lastly, creating layer masks pertains to controlling visibility and effects within a layer, which is unrelated to the task of adding crop marks.