@Nellybert , could be a button up shirt, when stress is put on the back of it and you have a front held together only by small spaced apart points it could open up
@Nellybert , going off of @Average Owl theory, it could also have been done up by snap on buttons, depending on how much wear and tear they've seen a breeze could pop them open.
Our teacher once said to us "do your work I'll be back in a Minute".
Five minutes later we look out the Windows of our Class room in the 4th floor, our teacher gets on his bike, looks up to us, shrugs his shoulders and Drives Home.
My first day of high school Spanish we were learning how to translate the days of the week. When the teachet wrote them down I asked if they should be capitalized, he answered "no", to which I replied "but that's not proper English".
The math teacher and the nail thing is the opposite of a problem.