Although there isn't a direct feature to create borders on Google Docs, there are 3 workarounds that you can use to create that appearance.

If you're looking to better organize your Google Doc, you should consider adding a table of contents. Here's how to do it.

Tables in Google Docs can be customized. This tutorial shows you how to Rotate and Color Google Docs Tables the easy way.

How to Make a Table in Google Docs. While the Google Docs spreadsheet program is essentially one large table, you may find a need for a table while creating a document or presentation.