In the story The Yellow Wallpaper by Charlotte Perkins Gilman

The function of the room is that of a literal and metaphorical prison. The bars on the window were meant to keep her shut in. Check out this quote,

It is a big, airy room, the whole floor nearly, with windows that look all ways, and air and sunshine galore. It was nursery first and then playroom and gymnasium, I should judge; for the windows are barred for little children, and there are rings and things in the walls.'