An automatic function that would put borders in your table in an automatic way.
You can do this a couple ways -
1. If you apply a table style that has a border, you’ll get a border on your tables
2. You can take #1 a step further by defining a table style (or customizing an existing one) to have a border you like, and then you can set that table style as the default table style.
Of course, you can also add a border around your table using the border button on the ribbon too (but it’s not automatic, and takes two clicks per table).