You can only define grids when you are creating a Gantt layout.
Use grids with Gantt layouts to view project activity information in a table format. You can customize field selections, fonts, and colors, optimize row widths and height for HTML fields, and optimize width and wrap text labels for plain text. You can stack fields, that is, set field to be in the same grid column. You can also filter, sort, and group the grid.
You can use the grid to create a list of activities and activity information quickly when you don't need to see the information graphically over time. You can group activities in categories that share a common attribute. For example, focus on activities by resource, responsibility, or date. Once you organize activities into groups, you can summarize or "roll up" project data to simplify their presentation. You can also sort activities to arrange them in an order you specify. For example, to view activities chronologically, you might sort them by early start date.
You can display line numbers for the grid.
You can include the Gantt chart with or without the grid, and set similar options for the Gantt as for the TSLD layouts.