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A double-breasted garment is a coat, jacket, or vest with wide, overlapping front flaps which has on its front two symmetrical columns of buttons; by contrast, a single-breasted item has a narrow overlap and only one column of buttons. In most modern double-breasted coats, one column of buttons is decorative, while the other is functional. The other buttons, placed on the outside edge of the coat breast, allow the overlap to fasten reversibly, left lapel over right lapel. To strengthen the fastening, a functional inner-button, called the jigger (or anchor button), is usually added to parallel-fasten the over-lapped layers together from the inside.
Suit jackets and blazers typically have one to four rows of buttons (each row containing two buttons), one or two of the rows functional. Each fastening method is identified using "number-on-number" terminology; the first number is the total number of front buttons, the second is the number of fastening buttons below the lapels (i.e. the second number also is the number of corresponding buttonholes). Six-on-two and six-on-one (as shown in the picture on the right) are the common button stances, but others exist. Stylistically, double-breasted suit jackets usually have peaked lapels, and fasten left lapel over right lapel as usual for men's jackets.
The original double-breasted jacket has six buttons, with three to close. This originated from the naval reefer jacket. Because shorter men may find that six buttons overwhelms their shorter torso, a four- or six-button configuration in which only the bottom one fastens may be a better option. The four-button double-breasted jacket that buttons at the lower button is often called the "Kent", after the man who made it popular—the Duke of Kent.
Double-breasted was the norm for frock coats during the 19th century. The early lounge suits that started to arrive around the turn of the 20th century, though, tended to be single-breasted. Ever since, single-breasted has been the norm for suit jackets.
Yet, double-breasted suit jackets were popular from the mid-1930s until the late 1950s, and again from the mid-1980s to the early 2000s. Today, double-breasted jackets are not as popular in the United States, and it is difficult to find them at many retail clothing stores. However, they continue to be popular in the United Kingdom, and in America are produced for and advocated by the high-end menswear lines of Joseph Abboud and Ralph Lauren, as well as by bespoke tailors such as Thomas Mahon; they have also seen a small comeback in European and American youth fashion, albeit in a slimmer, more modern cut.
Moreover, the overcoats—pea coat and trench coat—are traditionally double-breasted; the single-breasted versions being civilian interpretations of a military fashion. Due to the double-breasted jacket's construction, it is usually not recommended to wear a double-breasted lounge suit unbuttoned, unlike the single-breasted jacket, which can be left open or unbuttoned. This is because the large amounts of overlapping fabric on a double-breasted jacket tend to gather at the sides when unbuttoned. There are, however, formal jackets which are designed to be worn unbuttoned, with a vest: these are designed to avoid the perceived unsightly gathering (see Tailcoat).