To do Alt + h b s on Mac in Excel, download and install Accelerator Keys, then press Option, followed by h, b, and s.
Command: Outside Borders
This is how to do Alt + h b s on Mac in Excel with Accelerator Keys, the native ribbon and alt key shortcut solution for Mac users who get more done with Excel.
Alt + h b s activates the Outside Borders command in Excel, providing quick access to this feature from the ribbon.