In Excel, borders are applied to the shared edge between two cells, not to a single cell in isolation. If a cell appears to have no left or right border even after applying one, it is usually because the adjacent cell’s border setting on that shared edge is overriding it.
To fix this, format the entire range around that cell as one block so the shared borders are consistent:
- Select the problem cell and the cells immediately to its left and right (or the whole row/region where the issue appears).
- On the Home tab, in the Font group, select the arrow next to Borders.
- Choose a border style (for example, All Borders or a custom style via More Borders) so that the same border is applied consistently across all selected cells.
Key behaviors to keep in mind:
- When a border is applied to a selected cell, the border is also applied to adjacent cells that share that boundary. For example, if a box border is applied to B1:C5, cells D1:D5 acquire a left border.
- If two different border types are applied to a shared boundary, the most recently applied border is displayed.
- A selected range is formatted as a single block. If a right border is applied to B1:C5, it appears only on the right edge of C1:C5.
If the problem persists, select a slightly larger block around the cell (for example, several columns to the left and right) and reapply the desired border style to normalize all shared edges.
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