"Some women can achieve sexual pleasure simply by rubbing their legs together when wearing jeans. The friction created by the inner thighs on the jeans stimulates the clitoris. If you can maneuver your clitoris onto the inseam of your jeans, you may find that you can pleasure yourself just by rocking yourself or slightly rubbing your legs together"
(this comes from this great source http://www.female-masturbation-ejaculation.com/riding-the-seam.html )
My research shows this method is most popular among students and helpdesk staff but is just one way (not mentioned in the Masturbation FAQ ) that women fill their day. And aren't the men jealous.
How does a woman masturbate? - the answer may just be "better than men"!