How do you wear a suit jacket with 3 buttons?
There's a basic rule when it comes to buttoning up a suit jacket: "Sometimes, Always, Never" — if you have a three-buttoned jacket, sometimes button the top one, always button the middle one, and never button the bottom one. In a two-buttoned suit, you should always button the top button and never the second.
Why do some suits have 3 buttons?
Visual Effect: You might be surprised by how much of a difference one extra button can make on a suit. The three-button jacket has shorter lapels and a shallower V (especially compared to the two-button version).