You want to add a diagonal line across a table cell in Word to show a split heading, separate two variables, or mark a cell as not applicable. Standard table border tools in Word do not include a direct button for diagonal borders. This article explains how to use the Borders and Shading dialog box to apply a diagonal border to any table cell, and covers common mistakes that prevent the border from appearing correctly.
Key Takeaways: Diagonal Cell Borders in Word Tables
- Home tab > Paragraph group > Borders button > Borders and Shading: Opens the dialog where diagonal border options are available.
- Borders and Shading dialog > Borders tab > Apply to Cell: Ensures the diagonal border applies only to the selected cell, not the entire table.
- Diagonal Up and Diagonal Down buttons: Two distinct diagonal line styles you can apply individually or together to create an X.
How Diagonal Borders Work in Word Tables
Word’s table border tools are designed for horizontal and vertical gridlines. Diagonal borders are a hidden feature accessed through the Borders and Shading dialog box, not through the ribbon’s Table Design tab. The dialog provides two diagonal line options: Diagonal Up (from bottom-left to top-right) and Diagonal Down (from top-left to bottom-right). You can apply one diagonal line or both to create an X shape inside a single cell.
No prerequisites are required beyond a Word document containing a table. The feature works in Word for Microsoft 365, Word 2021, Word 2019, and earlier versions. The diagonal line is a cell border, not a drawn shape, so it behaves like any other border: it prints with the table, respects cell shading, and can be removed using the same dialog.
Steps to Apply a Diagonal Cell Border
The following steps show how to add a diagonal line to a single cell. You can repeat the process for multiple cells.
- Select the target cell
Click inside the table cell where you want the diagonal border. Do not select the entire table. If you select multiple cells, the border will apply to all selected cells. - Open the Borders and Shading dialog
Go to the Home tab. In the Paragraph group, click the small arrow next to the Borders button (the icon that looks like a four-square grid). From the dropdown menu, choose Borders and Shading at the bottom. - Switch to the Borders tab
In the dialog box that opens, click the Borders tab if it is not already selected. - Set Apply to Cell
At the bottom-right of the dialog, locate the Apply to dropdown. Select Cell. This ensures the diagonal border affects only the selected cell, not the entire table. - Choose the diagonal direction
In the Preview section on the right side of the dialog, you will see two diagonal buttons. Click the Diagonal Down button (the line that goes from top-left to bottom-right) or the Diagonal Up button (bottom-left to top-right). The preview shows the line immediately. To create an X, click both buttons. - Set line style, color, and width (optional)
Before clicking OK, you can change the diagonal line’s appearance. Use the Style, Color, and Width options on the left side of the dialog. These settings apply only to the diagonal border if it is selected in the preview. - Apply the border
Click OK to close the dialog. The diagonal line appears inside the selected cell.
After applying the border, you can type text in the cell. The diagonal line does not prevent text entry. If you need text on both sides of the line, use a text box or a separate shape instead.
Common Mistakes and How to Avoid Them
The diagonal border does not appear after clicking OK
The most common cause is that the Apply to option is set to Table instead of Cell. When Apply to is set to Table, the diagonal buttons are available but do nothing because a table cannot have a diagonal border across its entire grid. Always select Cell before clicking the diagonal buttons.
The diagonal border appears on the wrong cell or the whole table
This happens when you select multiple cells or the entire table before opening the dialog. Click inside a single cell only. If you already applied the border to the wrong area, select the correct cell, reopen the dialog, set Apply to Cell, and reapply the diagonal border.
Text is hidden behind the diagonal line
The diagonal border draws over the cell content. If the line overlaps your text, adjust the text position by adding spaces, line breaks, or using a smaller font size. For precise control, consider using a diagonal line shape from Insert > Shapes instead of a border.
Diagonal border disappears when merging cells
If you merge a cell that has a diagonal border with another cell, Word removes the diagonal border. Apply the diagonal border after merging cells, not before.
Diagonal Cell Border vs Alternative Methods
| Item | Diagonal Cell Border | Drawn Shape Line |
|---|---|---|
| Access method | Home > Borders > Borders and Shading | Insert > Shapes > Line |
| Resizes with cell | Yes, automatically | No, must be manually adjusted |
| Prints correctly | Yes | Yes |
| Supports text on both sides | No, line covers text | Yes, line can be sent behind text |
| Removal method | Dialog > remove diagonal buttons | Select shape and press Delete |
The diagonal cell border is best for simple visual separation where the line does not need to split text. For layouts that require text on both sides of the diagonal, use a drawn line and two text boxes or a table with two rows and a diagonal border applied to the merged cell.