Saw it on the street today, on the south side of M Street NW crossing 20th: guy in a rather sharp sportcoat1 with a single vent, in a kind of large houndstooth pattern. The vent2 was held shut by off-color manufacturer's twine designed to make the jacket hang well on the rack. This was visible from a hundred feet away.
Go home tonight and check all of your suit jackets, odd jackets3, and overcoats--anything with a vent--and make sure the twine is gone.
1. Just like a suit jacket, but without matching pants.
2. Any break in the jacket's bottom hem over the butt area. Single vent splits the middle of the butt, while a double-vented jacket has two vents, one on the outer edge of each buttock.
3. Term of art for "sportcoat".