Some pickpockets are very brazen and are know to pickpockets by slicing the pockets of of men and women's pants to gain access to their wallets, cash, or other valuables that is carried in pockets.  Typically these types of theft's are committed by "pocket slashers" who are thieves who use either a razor blade or small knife to cut the pocket.  Pocket slashers typically operate on buses, trains, or subways, where they can target victims who are sitting down.  The pocket slasher will sit right next to use and will many times use a coat, newspaper, or magazine as a "cover" when they are cutting your pocket.  What really works to the pocket slasher's benefit is a train or bus that has a lot of movement to help hide the "bumping" of the victim.

The follwing article will give you a first hand idea of how a pocket slasher works - read this article of pocket slashers.