Rule 4: Always button the waist button of your jacket. And only that button
Let’s start by defining the waist button. This is usually the middle button on a three-button suit, the top button on a two-button suit and obviously the only button on a one-button suit.
I say usually because this is the custom – it is the button that is placed at the individual’s waist, the place where the tailor has opted to place the waist and measure it. There are a few inches of play there from the bulge of your rib cage down to the top of your hip bone. There are high-waisted and low-waisted jackets, just as there are high-waisted and low-waisted trousers. The height of the waist button varies accordingly.
The whole structure of the jacket is built off this button and the shape of the shoulders. The lapels curl down to this button; the line of the suit from armhole to skirt is determined by the placement of this button. It is the fulcrum around which everything else revolves.
This is why men are always told to do up their suit jackets when standing. If they don’t, they might as well not wear a jacket that fits. All the tailoring is built off the shape created when the button is fastened.
The only thing that makes less sense is only doing up the bottom button. But I’ve written about that at length before. It makes me mad.
One quick and easy exception to the rule: weather is the main reason to do up the other buttons. For cold or for wind, you can legitimately fasten the other buttons to keep in heat or stop the skirt of your jacket flapping. This is the main reason I dislike one-button jackets – you don’t have that option.
The main exception to the rule, however, is true three-button jackets. Most three-button jackets have a lapel that is soft enough to roll back when the top button is left undone, leaving a straight line running down from the collar to the waist button. This is often referred to as a three-roll-two or three-roll-two and a half, because with the top button undone the jacket line looks almost like a two button.
Some jackets, however, are built with canvas in the lapels that keeps them stiff to the point of the top button. When only the middle button is done up, the line above is kinked, angling inwards where the lapel begins. There is no clean line to the collar.
Here, the top two buttons should be done up most of the time. That is how the line of the chest and the waist is designed, and the jacket will sit more naturally when fastened this way.
This is why this rule exists. And that is how to break it.