This is a handy little tip for when you are working with table borders in InDesign to hopefully make things just a little less fiddly. When you select the cells you want to work with the border tool appears in the info bar at the top of the page. This tool displays which borders on your selected cells will be affected by the changes you are about to make, any lines that are blue indicate borders that will be affected, any lines that are grey indicate borders that will not.