Dear Mr. Smith: On what angle should the outer pockets on a suit jacket be cut?This is my favourite kind of sartorial geekdom. What you ask about is the kind of detail that will be utterly unnoticeable to most people, but will subtly change the line of your suit.
Pockets on a mild angle - rising upward toward the front of the jacket - are a sign of a slightly racier suit, a suit that is a bit more tailored to the figure. Slant pockets are sometimes called hacking pockets, an English tradition that is an obscure reference to a kind of horse. (Some tailors will say hacking pocket to refer to an extra change pocket above the side pocket. The confusion arises from the fact that that pocket is also usually slanted.)
On very fashion-forward suits, the pocket may be slanted as much as 40 degrees, but that's quite flamboyant; most will not be tilted more than about 15 degrees. There is no rule, though: Boxier suits look fine with perfectly straight pockets. Note that slant pockets should always have a flap.
Flap pockets add a little bulk to a jacket, which is why dinner jackets, aiming to look sleek, bear the subtler "jetted" slit pockets; the jet is the narrow tape, usually in satin, sewn around the pocket edge. All good suits have "besom" pockets - that is, a narrow edge sewn in two lines around the slit. Ver well-tailored suits have both a flap and a besom, so that you can choose to tuck the flap into the pocket or not. Personally, I like to have the flaps out and showing; it looks slightly countrified, which is to say English.
Note that the outer breast pocket, the slit where you put your pocket square (never anything else) may also be slightly slanted, but in the opposite direction: It will be angled slightly down toward the lapel. This is to make up for the distortion caused by the curvature of the chest: It looks slanted on the hanger, but when you put it on, it looks straight.
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