How to change the borders format. You have bottom, top, left, and right border. No border, All borders, Outside borders, Thick Bottom border, also you have the same as Double border. There is shortcut for outside borders: Ctrl + Shift + &.
Step 1: Select cells.
Step 2: Click the Home tab > click the Bottom Border arrow.
Shortcut: Press Ctrl + Shift + & (for outside borders).