US morning television host Matt Lauer, recently fired from NBC's Today for sexually harassing women in terrible ways for years, had a door lock button under his desk. Who the hell installed that? we all wondered. But the answer may be: nobody. You can just buy one off Amazon.
Several commenters at the Root pointed this out. You can buy this one or this one, for example. One commenter noted that it seems to be common in some offices, so people don't walk in when you're doing normal person things like talking on the phone.
So that's cool, I guess.