You want to add diagonal lines inside specific table cells in Word to indicate split data, mark blank cells, or create a visual separator. Word does not include a one-click diagonal border button, but the feature exists inside the Borders and Shading dialog. This article shows the exact steps to apply diagonal borders to selected cells in a Word table, explains how to control line style and color, and covers common problems users encounter.
Key Takeaways: Adding Diagonal Borders to Word Table Cells
- Table Design > Borders > Borders and Shading: Opens the dialog where diagonal border options are located
- Apply To: Cell: Must be selected in the Borders and Shading dialog to restrict the diagonal line to only the chosen cells
- Custom diagonal line styles: You can change line weight, color, and apply both forward and backward diagonals in one cell
Understanding Diagonal Borders in Word Tables
Diagonal borders are lines drawn from one corner of a cell to the opposite corner. Unlike standard horizontal or vertical borders, diagonal borders split a cell diagonally without dividing the actual cell structure. Word stores this setting in the Borders and Shading dialog, not in the ribbon’s border gallery.
You can apply two types of diagonal borders:
- Forward diagonal (top-left to bottom-right) – often used to indicate a cell is intentionally left blank or to separate two data items.
- Backward diagonal (top-right to bottom-left) – used for the same purposes in the opposite orientation.
You can also apply both diagonals to create an X inside a single cell. Diagonal borders do not affect the cell’s content. Text and numbers remain in the cell and can be positioned manually above or below the line using line breaks or tab stops.
Steps to Apply Diagonal Borders to Specific Cells
These steps work in Word for Microsoft 365, Word 2021, Word 2019, and Word 2016. The interface is identical across these versions.
- Select the target cell or cells
Click inside the cell where you want the diagonal border. To select multiple cells, drag across them. Only the selected cells will receive the diagonal line. - Open the Borders and Shading dialog
On the ribbon, go to the Table Design tab. In the Borders group, click the small arrow icon in the bottom-right corner of the group. This opens the Borders and Shading dialog box. - Set the Apply To option to Cell
In the Borders and Shading dialog, at the bottom-right, locate the Apply To dropdown. Select Cell. If you leave this set to Table, the diagonal line will apply to the entire table border instead of individual cells. - Choose the diagonal direction
In the Preview section of the dialog, you see a small grid representing the cell. Two diagonal buttons appear to the left of the Preview grid. Click the top button for a forward diagonal (top-left to bottom-right). Click the bottom button for a backward diagonal (top-right to bottom-left). To add both diagonals, click both buttons. The Preview grid updates to show the line. - Adjust line style, color, and width (optional)
Before clicking the diagonal buttons, select your preferred Style (solid, dashed, dotted), Color, and Width from the controls on the left side of the dialog. The diagonal line uses the currently selected settings. If you change settings after clicking the diagonal buttons, you must click the diagonal button again to reapply the new style. - Apply the diagonal border
Click OK to close the dialog. The selected cells now display the diagonal border.
Common Mistakes and Limitations With Diagonal Borders
Diagonal border appears on the whole table instead of one cell
This happens when the Apply To option is set to Table instead of Cell. Open the Borders and Shading dialog again, change Apply To to Cell, and reapply the diagonal buttons. The diagonal line only affects the selected cells.
Diagonal border disappears after typing text
The diagonal line remains visible. Text does not remove the border. If the line seems to vanish, the cell may have a white or light background that hides a thin line. Increase the line width to 2.25 pt or higher in the Borders and Shading dialog to make the diagonal more visible.
Cannot add diagonal border to merged cells
Word does not support diagonal borders in merged cells. If you need a diagonal line in a merged cell, you must unmerge the cell first. Select the merged cell, go to the Layout tab under Table Tools, and click Split Cells. Then apply the diagonal border to one of the resulting individual cells.
Diagonal border does not print or appears misaligned
Check print preview before printing. If the diagonal line is missing, the printer driver may not support thin lines. Increase the line width to at least 1.5 pt and set the color to black. For alignment issues, ensure the cell has a fixed row height. Go to the Layout tab, open the Properties dialog, and set a specific row height under the Row tab.
Diagonal Border vs Standard Border: Key Differences
| Item | Diagonal Border | Standard Border |
|---|---|---|
| Direction | Corner to corner inside the cell | Along the edges of the cell |
| Purpose | Split cell visually without dividing data | Outline or separate cells |
| Apply To requirement | Must set Apply To to Cell | Works with Apply To set to Table or Cell |
| Merged cell support | Not supported | Supported |
| Text interaction | Text flows over the line; manual positioning needed | Text stays inside the border area |
You can now add diagonal borders to specific cells in Word tables using the Borders and Shading dialog. Start by selecting the cells, opening the dialog from Table Design, and setting Apply To to Cell before clicking the diagonal buttons. For a more polished look, combine forward and backward diagonals in a single cell and adjust line width to 2.25 pt for print clarity.