Microsoft Excel allows you to add borders around a cell or groups of cells to visually separate data values. By default, Excel uses a thin, black border, but allows you to select from various styles. By choosing a thicker, solid line, the border adopts a bold effect. This formatting option is available via the "Format Cells} window, which allows you to select the border type, color and position.
Open Microsoft Excel.
Click and drag your mouse pointer around the group of cells that will use the bold border.
Right-click any selected cell and choose "Format Cells."
Click the "Border" tab.
Click the thick, bold line, located in the "Style" section.
Click "Outline" under the Presets group to encase the selected cells in a border. For other border positions, click the corresponding position from the Border section, such as a top, buttom, left or right side border.