Watertown-based portrait photographer Brian Currier never set out to photograph flags. It wasn’t until his wife started putting together a portfolio for him to submit to a gallery that the theme emerged. But once it was pointed out to him how often there were flags in his images, he began to think about whether that was his way of compensating for his lack of military service - a responsibility that nearly all of the other male members of his extended family had taken on. The exhibit that resulted is called “The Fabric of a Year.’’ It is now on display at the Watertown Free Public Library.