Use the Borders command to apply or remove table cell borders.
Applying borders is a two-step process: First, choose line width and color options, and then select where to apply the borders. If borders are already applied, first select the cells that you want to change, and then choose a new border width and/or color.
The Borders drop-down menu on the Layout tab highlights the border options currently applied to the selected cells. The last option you selected from the menu is displayed in the command group, and acts as a toggle to add or remove the border style in selected cells.