Change a Gantt Chart's background lines
- Display the Gantt Chart, then choose View, Top Layout Options, Bars.
- Click Options.
- Click the General tab.
- To show background horizontal lines before every Summary bar, mark the Show Major Lines checkbox in the Horizontal Lines section.
- To show background horizontal lines at a specific interval of rows, mark the Show Minor Lines Every checkbox in the Horizontal Lines section, then type or select the row interval at which you want to the minor lines to be displayed.