Using Pillows to Masturbate?

I have hear people recommend to girls that they use pillows to masturbate ... can someone explain to me how that works? I don't really think through how you can do that with a pillow! its dirty, they basically rub themselves beside it then sleep on it next to their faces, not nice, dont do it,
be middle-of-the-road use your fingers - you have 10! lol.
you lay on it?? lol-