While defining fields on a form definition, you can choose Edit ð Field ð Delete latest selection or press Delete or F9 to remove a frame that you have drawn or double-clicked but not yet created a field definition for. This is useful if you make a mistake or change your mind about the size or position of the field.
If you are defining indexed fields, choose Delete latest selection or press Delete repeatedly to delete one field at the time in reverse order. That is, the red field (the one most recently drawn or double-clicked) is deleted, and the last green field becomes red. If you want to delete all marked fields at once (both red and green) press F9.