To hide or unhide specific rows or columns in Excel, you can take the following steps:

1. Select the rows or columns you want to hide.
2. Right-click the selection and choose Format Cells.
3. Under the Protection tab, uncheck the Locked box.
4. Go to the Review tab and click Protect Sheet.
5. Check the box next to ‘Select Locked Cells’ and click OK.
6. Your rows or columns will be hidden.