In the Advanced tab of the border window, you have the option to change the style, thickness, and color of the border separately for each side. In other words, users can modify the Right Side, Left Side, Bottom Side, and Top Side independently from one another.
Select the ellipsis button beside the border property in the Object Inspector.
Select the Advanced tab at the top of the window.
From here, select the settings you want to be applied to your borders. Once your selections have been made, select OK and close the window to update your borders.