I got the idea of starting this thread from the dreaded collar gap issue I've found in a couple of my suit coats. Of course it would be more interesting to talk about all of those other "difficult" fit issues like shoulder divots, collar roll that are rarely mentioned but sometimes can happen even in vintage garments. And, naturally, it would be appreciated to know if someone managed to fix these problems. I know that most people won't ever notice a collar gap, even if persisting in a neutral position. But I think that this is ad issue that once you note it, you'll end looking for it almost every time. I have a very nice 1930s suit with this problem, and I believe that is caused by the slighty sloped shape of the suit shoulders. It's a shame because I feel the coat tends to move away from the neck, in particular when I move. In another jacket I have this issue, but in a very slight way, only when I raise both arms forward. In this case I believe that shoulders shape is spot on, but probably the collar of the coat is a bit large for my neck, causing the lack of tension needed to keep it in place. Do someone can explain precisely what can be the reasons of this annoying imperfection? And has anyone experienced a way to fix it? For those who are not familiar with the term "collar gap", here's a picture of the awful situation: The jacket collar doesn't sit at the wearer's neck properly, giving the impression that the coat is "flowing" over the shoulders.