I had a coworker who felt free to interrupt me at any time. Even if I were frowning and leaning in to read some code word for word, he’d stop by to talk about nothing. I started wearing headphones when I was in concentration mode and that didn’t help. Then I wrote “DO NOT DISTURB” on a post-it note, stuck it to my headphones, and dug in for some thought-intensive hacking. He came to my desk, pulled the note off the headphones I wore, and tapped me on the shoulder, laughing. “Hah, look what someone taped to your head!”
We both learned something about the limits of my patience that day.