Have you ever wondered what the thin strip of metal or wood separating the panes in your window are called? Probably not, but in any case, theyre called muntins and, despite their ubiquity, they arent actually all that useful. Up until the mid-19th century, it was simply far more economical to produce smaller panes of glass for windows, making the muntin a necessary architectural aspect. Now, the practice of dividing windows, because weve been doing it for so long, is simply more architecturally attractive. These are not to be confused with the similar mullion, which are elements that separate entire windows, or else with astragal, which seal gaps between double doors love em or hate em, you've got weeks worth of windowed words over here.