“Fill down” refers to copying the pattern in the spreadsheet down a particular range in a column. For example if I type the number 1 in a cell and the number 2 in the cell below it and then highlight the two cells to signal the pattern, I can “fill down” to continue the pattern.
- Open a spreadsheet.
- Start adding a pattern of numbers or dates to a column or row.
- Highlight the cells. A small blue box appears in the lower-right corner.
- Click the blue box and drag it to select more cells where you want your data or text to repeat.
Here's a short video tutorial to help you get started with this feature: