A hacking jacket is a three-button, single-breasted
blazer that's usually made from
tweed. Usually the back has two parallel side vents as the hacking jacket was traditionally worn while riding (pleasure riding was known as "
hacking"). The double vents help the jacket back conform better to the
horse's back. The jacket also tends to button higher up. The buttons tend to cover chest level instead of covering the mid-
torso. This arrangement also helps the jacket sit properly on horse back.
Hacking jackets usually have pockets at an angle with a thick exterior
pocket flap. Again, the flap and angled opening are inspired by horseback riding. They keep things from flying out of the pockets while the horse bounces up and down.
Hacking jackets usually feature a
snugger fit than your normal
casual blazer. You don't want your jacket bouncing around when you ride. Many have an additional front pocket immediately above one of the standard two front pockets. This additional pocket is sometimes called a "
ticket pocket". The presence of a ticket pocket is a bit of a mystery. Ticket pockets were originally developed for 19th century British business men who rode trains a lot. As the name implies, it allowed a person to tuck his train ticket into it. Not many people go from horse to
train. It's likely as the hacking jacket became associated with the British country
squire look the ticket pocket was added to increase its British-ness for American buyers.