Since adding a theme switcher to my site, I’ve created several new simple themes, including a console theme. It is meant to look somewhat like a command line console / terminal. For this theme, regular borders didn’t fit in. I wanted something with repeated characters, looking more like some terminal application output or Markdown would have. Looking for doing this with pure CSS, a Stack Overflow answer helped me come up with a solution.
There is no way with the CSS content or the like to just have a character repeat to fill a given width or height. So the solution has us manually repeat the character in the content of a pseudo element enough times to handle our largest likely container. We position absolutely and use overflow: hidden to prevent our content from expanding our container and to cut it off at the appropriate length. With alignment and padding, we can then have repeating characters that line up properly in a monospace font grid.