Surprisingly enough, the variety of rear pocket options on pants exceeds even the possibilities of the front. You may have no pockets at all, one pocket or two, buttons or no buttons, flaps or simple welts–quite a bit of choice for something with minimal usefulness. Sure, you can put something in those rear pockets, but nothing much if you plan to do any comfortable sitting. As with most clothing design features, simpler means more formal, so dress pants would normally just have plain jetted rear pockets, perhaps with buttons. Once flaps enter the picture, the trouser becomes more casual. Rear patch pockets (again, think jeans) are especially casual.