You want to print the gridlines (gridlines: The horizontal and vertical lines that appear in many Project views. You can change the patterns and colors of gridlines, and you can control the interval at which different patterns and colors occur.) in a view, but they are not visible when you print your project.
Make sure the gridline color is dark enough to print clearly. Light gray, light blue, yellow, or white lines may not print clearly on black-and-white or color printers.
You can set gridline options for a task (task: An activity that has a beginning and an end. Project plans are made up of tasks.) report or a resource (resources: The people, equipment, and material that are used to complete tasks in a project.) report on the Details tab of the report's dialog box. On the Report menu, click Reports, select the report, and then click Edit.