The “Fill handle” is the little black box in the bottom right corner of the border of the active cell. You can use it to create series. If you give Excel two numbers to start, it will continue. Thus, if you enter 5 and 10; highlight those two cells; and click and drag using the fill handle, Excel will continue with 15, 20, 25, etc. Excel can calculate series using numbers, formulas, dates, times, and the names of days and months… but not other alphabetical text.